Name: face recognition and upside-down faces
Uploaded: 2023-04-30T06:46:13.000Z
Duration: 6 min 13 s
Channel: JoVE
Description: Face recognition is a specialized part of human perception. It often feels effortless, but it actually depends on complex and intensive processing. The brain uses dedicated networks to detect faces and tell them apart.

K12 Standards

new-york-state-science-learning-standards

New York State Science Learning Standards

High School

Life Science

Structure and Function

HS-LS1-2.

The Inverted-face Effect

1. 仪器设备与刺激材料
<ol>
	<li>本实验需要一台计算机和实验脚本编写软件。</li>
	<li>此外，实验还需要相对大量的面部图像，最好具有相似的光照条件且无表情。许多此类图像数据库均可在网上免费获取，供研究使用。一个良好的资源是麻省理工学院面部数据库：http://web.mit.edu/emeyers/www/face_databases.html#oulu</li>
</ol>
2. 设计
<ol>
	<li>准备一组 80 张面部图像，将其均分为两组，每组 40 张。将其中一组用于实验的无意识接触阶段，另一组保留用于测试阶段作为干扰项。
	<ol>
		<li>需确保两组中男性和女性的比例相同。例如，若一组 40 张图像中有 25 张男性面孔，则另一组也应有 25 张男性面孔。</li>
	</ol>
	</li>
	<li>无意识接触阶段程序
	<ol>
		<li>实验的第一部分是通过一个掩蔽任务，使被试无意识地接触 40 张面孔图像。</li>
		<li>实验开始时呈现“准备”屏幕，被试按下空格键后开始接触阶段。</li>
		<li>按下空格键后，40 张面孔图像将逐张呈现，每张持续 1 秒。每张图像之后会出现一个显示“男性/女性？”的屏幕（该任务要求被试判断面孔的性别）。</li>
		<li>设置程序，使被试按下 M 或 F 键（分别对应男性和女性）后自动进入下一张面孔。 图 1 示意了实验接触阶段的事件序列。</li>
		<li>该阶段共包含 40 个试验，每张面孔对应一个试验。</li>
	</ol>
	</li>
</ol>
<img alt="偶然编码与意外测试示意图，展示性别识别过程。" src="/files/ftp_upload/10209/10209fig1.jpg" data-altupdatedat="1761830439000" data-alt="图1"> 
图1. 用于演示倒置面孔效应的偶然编码记忆范式的实验方法。 实验分为两个部分。第一部分称为偶然编码阶段，参与者逐一观察一组40张面孔图像，并被要求仅判断每张面孔是男性还是女性。第二阶段为意外记忆测试。在每次试验中，两张面孔并排呈现，其中一张来自编码阶段所展示的面孔，另一张称为干扰项（foil），是观察者此前从未见过的新面孔。参与者需使用左右箭头键指出每对面孔中哪一张是之前见过的。关键在于，一半的面孔对以倒置方式呈现。关注的测量指标是参与者对正立面孔与倒置面孔的识别准确率。 <a href="https://www.jove.com/files/ftp_upload/10209/10209fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>
<ol start="3">
	<li>测试阶段程序
	<ol>
		<li>实验的测试部分也包含40个试次。</li>
		<li>在每个试次中，随机选择一张先前出现过的旧面孔和一张之前保留的面孔（同一性别），分别放置在屏幕的左侧和右侧。</li>
		<li>被试的任务是通过按左箭头键或右箭头键，判断成对面孔中哪一个是在之前见过的。</li>
		<li>关键的操作条件是，在一半的试次中，两张面孔以倒置方式呈现。</li>
		<li>将倒置和正立呈现的试次随机混合。</li>
	</ol>
	</li>
</ol>
3. 运行实验
<ol>
	<li>实验开始前，最好询问参与者是否存在已知的视觉障碍或困难，特别是，他们是否认为自己在识别人脸方面存在任何困难。</li>
	<li>让参与者坐在呈现计算机显示器前60 cm处。</li>
	<li>向参与者说明编码阶段的流程，但不要提及接下来的测试阶段：
	<ol>
		<li>“这是一项关于面部感知的实验。在每一次试验中，您将看到一张人脸，持续一秒钟，随后会出现一个屏幕，要求您判断刚才看到的人脸的性别。按M键表示男性，按F键表示女性。这项任务可能看起来非常简单，因为我们正在进行一项包含多个实验的研究，其中一些实验使用容易识别的刺激材料，而另一些则使用经过数字处理、更具挑战性的刺激材料。综合这些结果将有助于我们理解用于识别面部性别的面部特征。无论对您来说感觉容易还是困难，请尽最大努力完成。本阶段仅有40次试验，耗时不到五分钟即可完成。”</li>
	</ol>
	</li>
	<li>启动程序，并在参与者完成实验的这一阶段时在附近站立观察。</li>
	<li>当参与者完成后，请说出以下内容：
	<ol>
		<li>“感谢您完成研究的这一部分。接下来我希望您进行第二个实验，该实验也仅需五分钟。在每一次试验中，您将在屏幕左侧和右侧各看到一张人脸。每对人脸中，其中一张是您刚才见过的，另一张则是新的、未在您刚刚完成的判断任务中出现过的人脸。您现在的任务是识别出‘旧’人脸，即在之前的判断任务中出现过的那张脸。使用左箭头键选择左侧的人脸，右箭头键选择右侧的人脸。在部分试验中，两张人脸会以倒置方式呈现。这一点无关紧要——您的任务始终是尽可能准确地识别出您认为之前已经见过的那张人脸。”</li>
		<li>在参与者完成记忆测试时，在旁站立观察。</li>
	</ol>
	</li>
</ol>

发现倒置的面孔难以处理这一现象具有许多应用。例如，神经影像学研究利用这一效应来识别参与特异性面孔处理的脑区。当观察者观看正立和倒置的面孔时，会进行脑部扫描，随后比较对这两类刺激的反应。这两组刺激在整体上具有非常相似的视觉特性，导致视觉系统的大部分区域活动相似。然而，在一个脑区中，正立面孔引发的反应明显强于倒置面孔，这表明倒置面孔未能有效激活特异性的面孔处理神经元。以这种方式响应的脑区被称为梭状回，或梭状面孔区（有时简称为 FFA）。该脑区还被许多其他研究证实参与了面孔处理特异性方面的多种功能。
第二种应用涉及一种称为面孔失认症的疾病。该病表现为在识别、甚至有时在察觉面孔方面存在严重困难。面孔失认症可继发于梭状回的脑损伤。但现在已知，部分没有已知脑损伤病因的人群中也会出现该症状。评估面孔失认症的一种方法涉及倒置面孔效应。具体而言，面孔失认症患者不会表现出典型的倒置效应。尽管他们在识别倒置面孔时并不比正置面孔更困难，但他们总体上在识别正置面孔时存在显著障碍。这种缺乏倒置面孔效应的现象提示，面孔失认症是由于缺乏特化的面孔加...

倒置面孔效应

来源：Jonathan Flombaum 实验室——约翰斯·霍普金斯大学
在感知过程中，人们往往能够轻松地识别和理解复杂刺激，但这种能力实际上需要复杂而密集的加工过程。这是因为大脑对某些极为重要的刺激类型具有专门化且自动化的加工机制。其中最典型的例子就是面孔加工。人们无需刻意去察觉和识别面孔，这一过程似乎自然而然地发生。然而，检测面孔并区分不同面孔实际上是一项复杂的计算任务。

人类的面部识别能力依赖于特定的计算方式和专门的大脑网络。这种特异性的一个简单例证是倒置面孔效应。识别倒置的面孔远比识别正立的面孔困难得多，但这一现象在许多其他类型的视觉对象中并不存在。倒置面孔效应可通过多种方式进行演示。本视频展示了一种用于研究面部加工及倒置面孔效应的非刻意编码记忆范式。

为了分析结果，只需计算参与者在倒置面孔（上下颠倒）试验和正立面孔（正常朝向）试验中正确识别面孔的比例。使用条形图对表现进行比较，如图2所示。对于大多数视觉功能正常的观察者而言，识别正立面孔的准确率明显高于倒置面孔。然而，该任务具有较高难度，即使对于正立面孔，表现也可能低于0.9。而对于倒置面孔，表现可能接近随机水平（0.5），即观察者在每次试验中仅凭猜测所能达到的得分。在倒置面孔任务中表现较差表明，用于面孔识别的特异性计算过程和大脑机制经过优化，能够充分利用面孔通常以正立朝向呈现这一特点。
<img alt="直立与倒置面孔记忆准确率的柱状图。教育研究数据可视化。" src="/files/ftp_upload/10209/10209fig2.jpg" data-altupdatedat="1761830439000" data-alt="图 2"> 
图 2 倒置面孔与直立面孔的记忆准确率比较。 大多数视觉正...

来源：Jonathan Flombaum 实验室——约翰斯·霍普金斯大学  
在感知过程中，通常会出现能够识别和解释……的能力

我们并不试图去检测和识别人脸——它只是偶然地发生了。令人印象深刻的是，为了实现成功的识别，必须在特定的大脑网络中进行复杂且高要求的计算，以将各个独立的特征整合成一个连贯的面部图像。尽管识别正立的面孔相对容易，但识别倒置的面孔则要困难得多，即使这种情况并不适用于其他类型的视觉对象。这种现象通常被称为倒置面孔效应，被用于设计实验以研究面孔识别在认知层面以及大脑中的机制。本视频将演示如何设计和实施一项通过非刻意编码记忆范式研究倒置面孔效应的实验，以及如何分析和解释实验结果。在本实验中，要求参与者在两个不同阶段对男性和女性的面孔进行判断：即偶然接触阶段和测试阶段。在首次无意识接触阶段，向参与者逐一呈现一组40张面孔，每张面孔显示1秒。每张图像显示后，要求参与者通过按下相应的按键来报告该图像是男性还是女性。这一过程模拟了我们在无意中自然处理面孔的能力。接着，在第二个测试阶段，向受试者并列呈现两张人脸。其中一张随机选自无意识接触阶段，另一张称为干扰项（foil），与前者性别匹配且此前从未向受试者展示过。测试阶段的面孔也是随机混合呈现的，其中一半为倒置，另一半为正立。要求参与者指出之前见过的是其中哪一张面孔。在此情况下，因变量是正确识别出的面孔数量——一种简单的记忆准确性指标——针对正立和倒置两种朝向。当参与者看到正立的面孔时，其回忆先前见过的面孔的表现预计会优于倒置的面孔。识别倒置面孔时表现较差的现象被称为倒置面孔效应。开始实验前，需确认受试者无任何已知的视觉障碍或识别人脸的困难。首先，让受试者坐在距离显示计算机 60 cm 的位置。向其说明 incidental-exposure 阶段的指导说明，但不要提及即将进行的测试阶段。启动程序后，在参与者进行实验第一阶段并在5分钟内完成40次试验时，需在附近观察。注意，参与者会看到一张面孔持续1秒，并通过按“M”键表示男性，或按“F”键表示女性，以判断该面孔的性别。完成初始阶段后，感谢参与者完成本部分研究，并告知他们下一测试阶段的说明。再次启动程序，并在旁边站立，观察参与者完成包含40次试验的第二记忆阶段。在此部分，请注意参与者按左箭头键或右箭头键，以指示先前观察到的是哪一张面孔。要分析数据，只需计算正确识别的人脸比例，并按试验类型（正立与倒立）绘制记忆准确性的结果图。请注意，对于大多数视觉正常的参与者而言，识别正立面孔的准确率远高于倒置面孔，这表明了倒置面孔效应。对倒置面孔识别表现较差，接近随机水平，表明专门的面部加工机制经过调适，以利用面孔几乎总是以正立朝向呈现这一特点。现在您已经熟悉了处理倒置面孔所涉及的复杂性，接下来让我们探讨其他可以应用该效应的研究场景。神经影像学研究已采用倒置面孔效应来识别参与特异性面孔加工的脑区。正立的面孔比倒置的面孔在梭状回面孔区（FFA）引发更强的神经反应，表明倒置的面孔无法有效激活专门的面孔加工神经元。此外，FFA 区域的脑损伤可能导致一种称为面孔失认症的疾病——即无法识别人脸，包括自己的面孔。该任务常用于诊断脸盲症，因为脸盲症患者在识别正立面孔时通常与识别倒置面孔一样困难。您刚刚观看了 JoVE 关于倒置面孔效应的介绍。现在，您应该已经充分了解如何通过呈现一系列面孔并依靠记忆识别熟悉面孔的方法，来设计和实施此类实验。您还应掌握如何分析和解释实验结果。感谢观看！

Education

教育

JoVE Science Education

Psychology

心理学

Sensation and Perception

感觉与知觉

倒面效应

face recognition and upside-down faces

Face recognition is a specialized part of human perception. It often feels effortless, but it actually depends on complex and intensive processing. The brain uses dedicated networks to detect faces and tell them apart.

Face Recognition and Upside-Down Faces

color afterimages

Color Opponency and Afterimages

Color afterimages show how the brain uses opponent color signals to process vision. Human color vision can separate millions of hues, even though it depends on fairly simple hardware. A key part of that ability comes from an opponent system in the brain. In an opponent system, the presence of one kind of color signal is treated as evidence for the absence of another. The absence of one signal can also count as evidence for the other. For example, some brain cells respond when blue is present...

finding your blind spot and perceptual filling-in

finding-your-blind-spot-and-perceptual-filling-in

How the Brain Fills In the Blind Spot

The blind spot is a gap in vision created by the retina and optic nerve. The retina contains light-sensitive cells that detect light and send signals to the brain through the optic nerve, a bundle of neural fibers. In each retina, there is one area in the periphery where these outputs collect and the optic nerve exits. That spot has no photosensitivity, so light that lands there does not create a signal. This means humans have a blind spot, or a place in the visual field where incoming stimuli...

perspectives on sensation and perception

Sensory Illusions in Perception

Sensation and perception explain how the brain turns sensory signals into what we see, hear, feel, and taste. Sensation is the process of transducing signals from sensory organs, such as the eyes. Perception is how the brain interprets those messages. This field has a long history that reaches back to the 19th century. During that time, scientists made major progress in understanding the properties of light and how they connect to the visual system. Those findings helped shape modern ideas...

motion-induced blindness

Visual Awareness Through Motion Illusion

Visual awareness and motion-induced blindness show how the brain shapes what people see. In visual perception and sensation, what appears in the world is not a direct copy of physical reality. People may miss real objects, see things that are not there, or see them in a distorted way. Scientists use the word awareness to mean what people actually perceive. To study awareness, vision researchers often rely on illusions and misperceptions. These cases help reveal how the brain builds experience...

the rubber hand illusion

Body Mapping and the Rubber Hand Illusion

The Rubber Hand Illusion shows how the brain builds a map of the body in space. This body map helps people reach for objects, walk without hitting obstacles, and sit down without missing a chair. It depends on proprioception, which is the brain's sense of where the limbs are based on control and feedback signals. The brain does not rely on proprioception alone. It also uses vision, touch, and even sound to represent body parts in space. The classic illusion, first described by Botvinick and...

the ames room

How the Ames Room Warps Depth

The Ames Room is a visual illusion that changes how people judge depth and size. It is built to show how the brain uses assumptions to recover three-dimensional space from a two-dimensional image on the retina. The retina is the light-sensitive tissue inside the human eye. Light from objects in the world reflects onto the retina and creates patterns of stimulation. Objects that are side-by-side in the world usually create side-by-side stimulations on the retina. Distance is harder to recover,...

inattentional blindness

Visual Attention and Missed Objects

Visual attention helps determine which parts of the visual world the brain processes and how well it processes them. Because attention is limited, people cannot take in everything at once, even when an object is right in front of them. Researchers began showing this effect in the 1960s. Ulrich Neisser demonstrated that people can miss visible objects when their attention is distracted. Later, in the 1980s and 1990s, Arien Mack and Irvin Rock built on that work and developed a simple way to...

spatial cueing

Measuring Visual Attention with Cues

Visual attention is the limited ability to focus on some information while ignoring other stimuli in the environment. It is studied in many senses, including vision, hearing, touch, taste, and smell. Researchers most often examine it in vision because it is easy to test with controlled displays. A common method is the spatial cueing paradigm. In this task, a cue appears to guide attention toward one location, and researchers measure what happens when attention is focused there instead of...

the attentional blink

Measuring Visual Attention Lapses

Visual attention is needed to recognize a stimulus. Early in vision, objects are not seen as whole objects. They are processed as features such as lines, corners, texture changes, color, and light. Attention helps later processing combine those features into something the brain can identify. This makes attention a major topic in vision research. A key question is how people sustain attention over time. Sustained attention means keeping focus from moment to moment. It takes effort, especially...

crowding

Peripheral Vision and Letter Crowding

Peripheral vision and letter crowding are shown in this high school science video. The lesson connects how the eye samples light with why objects are harder to recognize at the edge of vision. Human vision depends on light-sensitive neurons in the back of the eye called the retina. These neurons are rods and cones, named for their shapes. They are not spread evenly across the retina. The center region, called the macula, has a dense pack of cones. Cones are especially concentrated in the...

the inverted-face effect

Face recognition is a specialized part of human perception. It often feels effortless, but it actually depends on complex and intensive processing. The brain uses dedicated networks to detect faces and tell them apart.

the mcgurk effect

How Lip Reading Shapes Speech Perception

Speech perception depends on both hearing and vision. In many face-to-face conversations, the mouth gives strong visual clues about what a person is saying. Those clues can help the brain sort out speech sounds that are hard to hear clearly. This reliance on visual input is one reason spoken language is easier to understand when the speaker’s face is visible and close up. The mouth can sometimes provide better information than the sound alone. When the brain combines what it sees with what it...

just-noticeable differences

Measuring Size Changes with JND

Psychophysics studies how physical changes become neural signals and mental ideas about magnitude. A key idea in this field is the just-noticeable difference, or JND. A JND is the smallest change people can perceive. Size is a clear way to study JND. Small changes in a child’s height may go unnoticed from day to day. After a longer absence, such as a return from sleep-away camp or a visit after many weeks, those same small changes can seem obvious because they have added up. Researchers...

the staircase procedure for finding a perceptual threshold

the-staircase-procedure-for-finding-a-perceptual-threshold

Measuring Auditory Thresholds with Staircase Testing

Psychophysics studies how the physical strength of a stimulus relates to what people actually perceive. It focuses on perceptual thresholds, which are the smallest amounts of stimulation a person can sense. Examples include the brightness needed to see a light, the pressure needed to feel touch, and the softness of a sound that can still be heard. The staircase procedure is an efficient method for finding a perceptual threshold. Here, the stimulus is adjusted step by step based on a person’s...

object substitution masking

Visual Masking with Object Substitution

Visual masking describes cases where one image is presented, but an observer does not perceive it because a second image appears. In vision science, this kind of interference helps researchers study how the brain selects and stores visual information. Object substitution masking is a surprising form of visual masking. It became an important topic in vision research after it was discovered relatively recently, around 1997, by Enns and Di Lollo. The effect has been studied because it shows that...

sensation and perception

这本文集探讨了各种程序, 研究如何大脑处理我们复杂的感官世界, 解决问题的意识意识和视觉, 触觉, 和听觉感知。

Explore how the brain processes faces and why upside-down faces are harder to recognize. Learn the inverted-face effect through incidental memory testing.

Face Recognition and Upside-Down Faces | JoVE K12

Jonathan Flombaum

Overview

Experimental Design

Running the Experiment

Representative Results

Applications

Summary

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

https://cloudfront.jove.com/files/media/science-education/science-education-thumbs/10647.jpg

Cell Structure

Background
Cells represent the most basic biological units of all organisms, whether it be simple, single-celled organisms like bacteria, or large, ...

Visualizing Onion and Cheek Cells
ExpandImmediately before the experiment, wash and peel onion bulbs for the class.
Remove the entire brown outer skin and ...

Visualizing Onion and Human Cells
ExpandIn this experiment you will prepare different types of cells from a plant and animal, onion and human ...

What are Cells?

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

Cytoplasm

The cytoplasm consists of organelles and a framework of protein scaffolds called the cytoskeleton suspended in an aqueous solution, the cytosol. The ...

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression ...

The Central Dogma

The DNA Helix

Nucleic Acids

DNA as a Genetic Template

Structure of a Gene

A gene is the fundamental unit of heredity. Every individual has two copies of each gene, one inherited from each parent. Although most people contain the ...

Chromosome Structure

Base-pairing and DNA Repair

What is Gene Expression?

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is comprised&#160; of nucleotides and proteins are ...

RNA Structure

The basic structure of RNA consists of a string of ribonucleotides attached by phosphodiester bonds. Although most RNA is single-stranded, it can form ...

Types of RNA

Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse ...

Transcription

Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Translation

Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes ...

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Protein and Protein Structures

Proteins: From Genes to Degradation

From DNA to Protein

The flow of genetic information in cells from DNA to mRNA to protein is described by the central dogma, which states that genes specify the sequence of ...

Protein Folding

Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to ...

An Overview of Gene Expression

Gene expression is the complex process where a cell uses its genetic information to make functional products. This process is regulated at multiple ...

an-introduction-to-caenorhabditis-elegans

An Introduction to Caenorhabditis elegans

Caenorhabditis elegans is a microscopic, soil-dwelling roundworm that has been powerfully used as a model organism since the early 1970&rsquo;s.  It was ...

An Overview of Genetic Analysis

An organism&#8217;s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its ...

An Introduction to Cell Death

Necrosis, apoptosis, and autophagic cell death are all manners in which cells can die, and these mechanisms can be induced by different stimuli, such as ...

An Overview of Genetic Engineering

Genetic engineering &#8211; the process of purposefully altering an organism&#8217;s DNA &#8211; has been used to create powerful research tools and model ...

An Introduction to Cell Division

Cell division is the process by which a parent cell divides and gives rise to two or more daughter cells. It is a means of reproduction for single-cell ...

An Overview of Genetics and Disease

Many human diseases are associated with mutations or variations in genetic sequences. Some of these genetic variants are heritable, passed down from ...

an-introduction-to-cellular-and-molecular-neuroscience

An Introduction to Cellular and Molecular Neuroscience

Cellular and molecular neuroscience is one of the newest and fastest growing subdisciplines in neuroscience. By investigating the influences of genes, ...

Annexin V and Propidium Iodide Labeling

Staining with annexin V and propidium iodide (PI) provides researchers with a way to identify different types of cell death&#8212;either necrosis or ...

an-introduction-to-developmental-genetics

An Introduction to Developmental Genetics

Development is the complex process through which a single-celled embryo transforms into a multicellular organism. Developmental processes are guided by ...

Bacterial Transformation: Electroporation

The term &#x201C;transformation&#x201D; refers cellular ingestion of foreign DNA.  In nature, transformation can occur in certain types of bacteria.  In ...

an-introduction-to-molecular-developmental-biology

An Introduction to Molecular Developmental Biology

Molecular signals play a major role in the complex processes occurring during embryonic development. These signals regulate activities such as cell ...

bacterial-transformation-the-heat-shock-method

Bacterial Transformation: The Heat Shock Method

Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of ...

an-introduction-to-saccharomyces-cerevisiae

An Introduction to Saccharomyces cerevisiae

Saccharomyces cerevisiae (commonly known as baker&rsquo;s yeast) is a single-celled eukaryote that is frequently used in scientific research.  S. ...

Cell Cycle Analysis

Cell cycle refers to the set of events through which a cell grows, replicates its genome, and ultimately divides into two daughter cells through the ...

An Introduction to Transfection

Transfection is the process of inserting genetic material, such as DNA and double stranded RNA, into mammalian cells. The insertion of DNA into a cell ...

Chromatin Immunoprecipitation

Histones are proteins that help organize DNA in eukaryotic nuclei by serving as &#8220;scaffolds&#8221; around which DNA can be wrapped, forming a complex ...

An Overview of Epigenetics

Since the early days of genetics research, scientists have noted certain heritable phenotypic differences that are not due to differences in the ...

community-dna-extraction-from-bacterial-colonies

Community DNA Extraction from Bacterial Colonies

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
Traditional methods of analysis ...

Cytogenetics

Cytogenetics is the field of study devoted to chromosomes, and involves the direct observation of a cell&#8217;s chromosomal number and structure, ...

embryonic-stem-cell-culture-and-differentiation

Embryonic Stem Cell Culture and Differentiation

Culturing embryonic stem (ES) cells requires conditions that maintain these cells in an undifferentiated state to preserve their capacity for self-renewal ...

DNA Gel Electrophoresis

DNA gel electrophoresis is a technique used for the detection and separation of DNA molecules. An electric field is applied to a gel matrix comprised of ...

Enzyme Assays and Kinetics

Enzyme kinetics describes the catalytic effects of enzymes, which are biomolecules that facilitate chemical reactions necessary for living organisms. ...

DNA Ligation Reactions

In molecular biology, ligation refers to the joining of two DNA fragments through the formation of a phosphodiester bond.  An enzyme known as a ligase ...

explant-culture-for-developmental-studies

Explant Culture for Developmental Studies

Explant culture is a technique in which living cells or tissues are removed from an embryo for continued development outside of the organism. This ex vivo ...

DNA Methylation Analysis

Methylation at CpG dinucleotides is a chemical modification of DNA hypothesized to play important roles in regulating gene expression. In particular, the ...

Expression Profiling with Microarrays

Microarrays are important tools for profiling gene expression, and are based on complementary binding between probes that are attached to glass chips and ...

Density Gradient Ultracentrifugation

Density gradient ultracentrifugation is a common technique used to isolate and purify biomolecules and cell structures. This technique exploits the fact ...

F&#246;rster Resonance Energy Transfer (FRET)

F&#246;rster resonance energy transfer (FRET) is a phenomenon used to investigate close-range biochemical interactions. In FRET, a donor photoluminescent ...

detecting-environmental-microorganisms-with-polymerase-chain-reaction

Detecting Environmental Microorganisms with the Polymerase Chain Reaction and Gel Electrophoresis

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
Demonstrating Author: Bradley Schmitz
Polymerase chain reaction (PCR) is ...

Gel Purification

Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, ...

Detecting Reactive Oxygen Species

Reactive oxygen species are chemically active, oxygen-derived molecules capable of oxidizing other molecules. Because of their reactive nature, there are ...

Gene Silencing with Morpholinos

Morpholino-mediated gene silencing is a common technique used to study roles of specific genes during development. Morpholinos inhibit gene expression by ...

development-and-reproduction-of-the-laboratory-mouse

Development and Reproduction of the Laboratory Mouse

Successful breeding of the laboratory mouse (Mus musculus) is critical to the establishment and maintenance of a productive animal colony. Additionally, ...

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

HS-LS1-1.

Face Recognition and Upside-Down Faces

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