Arendell Parrot Academy

AP PSYCHOLOGY Mrs. Anne Nuckolls

Internet was unavailable at school this afternoon and at home this evening.  I apologize for the delay but you are prepared for this assessment.

Remember:  

1. As always, your notecards are due tomorrow.  

2. All terms are fair game so make certain that you understand the definition...not by recognition or recall but by application.

3.  The assessment will only pertain to the information listed here, all terms from the unit, the 4 people identified at the end of the list...we have discussed each one...

4.  Terms not in bold in our text but are important include phenotype, sex chromosome versus autosomal chromosomes,  and SNP's (their role). 

Genetic Similarity: We All Have the Same Genes Each person has the same set of genes - about 20,000 in all. The differences between people come from slight variations in these genes. For example, a person with red hair doesn't have the "red hair gene" while a person with brown hair has the "brown hair gene." Instead, all people have genes for hair color, and different versions of these genes dictate whether someone will be a redhead or a brunette.

 

The Basics of DNA      Your body contains 50 trillion tiny cells, and almost every one of them contains the complete set of instructions for making you. These instructions are encoded in your DNA. DNA is a long, ladder-shaped molecule. Each rung on the ladder is made up of a pair of interlocking units, called bases, that are designated by the four letters in the DNA alphabet.A

 

DNA is Organized Into Chromosomes

The long molecules of DNA in your cells are organized into pieces called chromosomes. Humans have 23 pairs of chromosomes. Other organisms have different numbers of pairs - for example, chimpanzees have 24 pairs. The number of chromosomes doesn't determine how complex an organism is - bananas have 11 pairs of chromosomes, while fruit flies have only 4.

 

Chromosomes are Organized Into Genes

Chromosomes are further organized into short segments of DNA called genes. If you imagine your DNA as a cookbook, then your genes are the recipes. Written in the DNA alphabet - A, T, C, and G - the recipes tell your cells how to function and what traits to express. For example, if you have curly hair, it is because the genes you inherited from your parents are instructing your hair follicle cells to make curly strands.

 

Genes Make Proteins

Cells use the recipes written in your genes to make proteins - just like you use recipes from a cookbook to make dinner. Proteins do much of the work in your cells and your body as a whole. Some proteins give cells their shape and structure. Others help cells carry out biological processes like digesting food or carrying oxygen in the blood. Using different combinations of the As, Cs, Ts and Gs, DNA creates the different proteins - just as you use different combinations of the same ingredients to make different meals.

 

Genetic Switches Control the Traits Cells Express

Cells come in a dizzying array of types; there are brain cells and blood cells, skin cells and liver cells and bone cells. But every cell contains the same instructions in the form of DNA. So how do cells know whether to make an eye or a foot? The answer lies in intricate systems of genetic switches. Master genes turn other genes on and off, making sure that the right proteins are made at the right time in the right cells.

 

SNPs are Copying Errors     To make new cells, an existing cell divides in two. But first it copies its DNA so the new cells will each have a complete set of genetic instructions. Cells sometimes make mistakes during the copying process - kind of like typos. These typos lead to variations in the DNA sequence at particular locations, called single nucleotide polymorphisms, or SNPs (pronounced "snips").

 

The Consequences of SNPs

SNPs can generate biological variation between people by causing differences in the recipes for proteins that are written in genes. Those differences can in turn influence a variety of traits such as appearance, disease susceptibility or response to drugs. While some SNPs lead to differences in health or physical appearance, most SNPs seem to lead to no observable differences between people at all.

 

SNPs as a Measure of Genetic Similarity

DNA is passed from parent to child, so you inherit your SNPs versions from your parents. You will be a match with your siblings, grandparents, aunts, uncles, and cousins at many of these SNPs. But you will have far fewer matches with people to whom you are only distantly related. The number of SNPs where you match another person can therefore be used to tell how closely related you are.

Chromosomes are Inherited From Your Parents   One chromosome from each of your 23 pairs came from each of your parents. The two chromosomes of a pair (except for the sex chromosomes) contain the same genes, but the genes have small differences. Things like SNPs make each copy of a gene uniquely Mom's or Dad's.

 

The X and Y Chromosomes Determine Your Sex

One chromosome pair - the sex chromosomes - is unique. You don't necessarily end up with a matching pair. Typically females have two X chromosomes and males have an X and a Y. Mothers always pass an X chromosome on to their children. Whether your father passes on his X chromosome (leading to a pair of X chromosomes) or his Y chromosome (making a mixed set) determines your sex.

 

Chromosomes Get Shuffled When Eggs and Sperm are Made

Though most adult cells contain two sets of chromosomes, sperm and egg cells are different. These special cells have just one chromosome from each pair. Which chromosome they get from each pair is random, making each sperm or egg cell unique. There is also a bit of mixing before the chromosomes are sorted into individual sperm or egg cells. Chromosomes from each pair in a mother or father, respectively, make contact and exchange pieces of DNA, creating hybrid chromosomes.

 

Egg and Sperm Combine to Create a Child

When a sperm and egg cell join together at fertilization they create a single cell with two complete sets of 23 chromosomes. This single cell divides to create new cells, over and over, forming the body of developing child. This is how you came to be you. If you have siblings, the same events created them. But because the egg and sperm production processes are random, your siblings didn't get the same set of chromosomes from each of your parents that you did (unless you happen to be an identical twin).

 

Using DNA to Trace Ancestry

Because the chromosomes mothers and fathers pass on to their children are reshuffled versions of the ones they inherited from their own parents, it is hard to use most chromosomes to trace genealogy back very far. Most of the Y chromosome, however, is handed down from father to son without changes. Likewise, in humans, the tiny bit of DNA contained in an unusual package of genetic material known as mitochondrial DNA is passed down from mother to child without any recombination. For this reason, these types of DNA can be used to trace your ancestry.

Observable Traits are the Result of Gene and Environment Interactions   Your observable traits, also known as your phenotypes, result from interactions between your genes and the environment. Differences in some phenotypes, like height, are determined mostly by genes. If you have short parents and grandparents, you probably don't tower over your peers, though environmental factors like a healthy diet might give you a little lift. The influence of genes on other traits, such as your personality, is less well understood.

 

 

SNPs Can Affect Your Phenotype   Every day, scientists are learning more and more about how aspects of your DNA, especially SNPs, affect your phenotype. Some SNPs have been linked to health issues. Others have been linked to fun and interesting things you might never have even considered - such as whether you like Brussels sprouts or what kind of earwax you have.

 

 

You Can Learn About 1 Million SNPs All at Once  Learning about your DNA can help you to understand a little better why you are the way you are, and in what ways you're similar to or different from your family, friends, and neighbors. Scientists can now analyze more than 1,000,000 SNPs in your genome.

 

 

 

Counting out chromosome numbers

For example, humans have 46 total chromosomes. These chromosomes come in two varieties:

•    Sex chromosomes: These chromosomes determine gender. Human cells contain two sex chromosomes. If you're female, you have two X chromosomes, and if you're male, you have an X and a Y chromosome.

•    Autosomal chromosomes: Autosomal simply refers to non-sex chromosomes. So, sticking with the human example, do the math, and you can see that humans have 44 autosomal chromosomes.

Ah, but there's more. In humans, chromosomes come in pairs. That means you have 22 pairs of uniquely shaped autosomal chromosomes plus 1 pair of sex chromosomes, for a total of 23 chromosome pairs. Your autosomal chromosomes are identified by numbers — 1 through 22. So, you have two chromosome 1s, two 2s, and so on.

When chromosomes are divided into pairs, the individual chromosomes in each pair are considered homologous, meaning that the paired chromosomes are identical to one another in shape and size.

For example, your two single chromosome 2s are paired up because they're identical in shape and size. These are homologous chromosomes.

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Examining chromosome anatomy

The differences in shapes and sizes of chromosomes are easy to see, but the most important differences between chromosomes are hidden deep inside the DNA.

Chromosomes carry genes.

Genes are sections of DNA that make up the building plans for physical traits.

The genes tell the body how, when, and where to make all the structures that are necessary for the processes of living.

Each pair of homologous chromosomes carries the same — but not necessarily identical — genes.

For example, both chromosomes of a particular homologous pair might contain the gene for hair color, but one can be a "brown hair" version of the gene — alternative versions of genes are called alleles — and the other can be a "blond hair" allele.

Any given gene can have one or more alleles. The alleles code for the different physical traits (phenotypes) you see in animals and plants like hair color or flower shape.

Most of the phenotypes that you see are produced by multiple genes (that is, genes occurring at different loci and often on different chromosomes) acting together. For instance, human eye color is determined by at least three different genes that reside on two different chromosomes.

 

Mapping ourselves: The Human Genome Project

 

You've probably heard about this project on the news, even if you didn't know what a genome was at the time. (By the way, a genome is the total collection of genes in a species.) In 1988, laboratories all across the world began determining the DNA sequences of human DNA.

If you are wondering why the Human Genome Project is a big deal, think of it this way. If you were a researcher and you wanted to study a specific human gene, first you would have to know what chromosome it "lived" on. To provide the "address" of each human gene, researchers set out to build a map of the nucleotide sequences in the DNA of each human chromosome.

Sounds like a daunting task, doesn't it? Well, the process of DNA sequencing became automated, and with several laboratories around the country all working toward the same goal and sequencing different pieces of DNA using really sophisticated computer programs, the project was largely completed several years ahead of schedule — how often does that happen?

Now armed with a roadmap of where every gene is located, researchers can turn their attention toward making good use of that information. Knowing where each gene resides in the chromosomes, the "bad" genes — the ones that cause disease or cancer or other undesirable traits — can be sought out. Gene therapy research is trying to prevent the bad genes from having their undesirable effect or to convert them to good genes. It is predicted that the future of medicine will heavily use gene therapy to prevent the occurrence of diseases rather than medicines to treat diseases that have already taken hold.

However, now that research is dealing with human genes, plenty of controversy is peppering the positive results. An uproar in the 1980s occurred when a genetically engineered strawberry was created. As geneticists, biochemists, and molecular cell biologists discover more about what can be done with genetic information, others are worried about the implications of such technology. Even after gene therapy has been successfully used, people just are not sure how to approach the future. 

What is a mutation?

Each gene is made up of a series of bases, and those bases provide instructions for making a single protein. Any change in the sequence of bases — and therefore in the protein instructions — is a mutation. Just like changing a letter in a sentence can change the sentence's meaning, a mutation can change the instruction contained in the gene. Some mutations have little or no effect on the protein, while others cause the protein not to function at all.   Famous People:   Thomas Bouchard Minnesota Twin Study

Charles Darwin: Evolution, “Survival of the Fittest”

David Buss Evolutionary Psychology Researcher, extending Darwin’s advances

 

Dr. Francis Collins:  physician-geneticist noted for his landmark discoveries of disease genes and his leadership of the international Human Genome Project, which culminated in April 2003 with the completion of a finished sequence of the human DNA instruction book. He served as director of the National Human Genome Research Institute at the NIH from 1993-2008.

 

Unit 3C