General Biology Lab 100 (SDSU): Exam 3

What are the major structural units of DNA?

phosphate, sugar and base for a nucleotide which pairs to another nucleotide

What kind of bond holds the backbone of DNA together

a strong phosphate bond

What are the four bases in DNA

Adenine, Thymine, Cytosine, Guanine

which bases are complimentary

Adenine-Thymine (A-T)

Cytosine-Guanine (C-G)

What kind of bond holds the bases together in DNA

a weak hydrogen bond

How does DNA replicate?

semi conservatively: exact daughter DNA consists half of parental DNA and half of new DNA: the new strands are identical

Are both strands of DNA pointed in the same direction

no they are pointed in opposite directions so they can face each other on the base side and pair together

Where is DNA usually recovered at a crime scene

on the body or anywhere in the crime scene really

Can you obtain DNA from a fingerprint

yes but it is not entirely reliable

What is DNA fingerprinting?

identifies the unique patterns in an individual's DNA

What enzyme is used in DNA fingerprinting

restriction enzymes

What are hypervariable regions?

Three sequences of amino acids with pro-found variability located within the variable regions of both heavy and light chains. They are responsible for the specificity of antibodies.

How do we compare DNA from one person to another

by looking at the sizes of the DNA fragments

What does DNA tell us about a suspect

that they were at the scene

can we determine guilt from DNA evidence

no, it only proves the person was at the scene

What is gel electrophoresis?

the separation of charges molecules using an electric field

What property of DNA allows E-gel to work

the variable sizes of the bases

How is E-gel process related to the diffusion seen in lab 4?

It separates molecules by size

How can DNA fingerprinting be used to prove paternity

half the parents genes would match the child's-- there would be a definite similarity

How similar is the DNA between a parent and their child

50% the same

How similar is the DNA of two children with the same parents?

about 50% at the most

How similar is the DNA of identical twins

very similar but not identical

can you tell what sort of DNA is used in an E-gel test if you only see the end results?

no

What state do cells spend most of their time in

interphase

When does DNA synthesis occur?

Interphase

What is the purpose of cellular division

to make and replace cells

what are the four stages of cellular division

prophase, metaphase, anaphase, telophase

Do all cells that divide go through mitosis?

yes

do all cells that divide go through meiosis

no, only reproductive cells

what are the differences between mitosis and meiosis

meiosis happens during reproduction in reproductive cells-- it starts with diploid cells and ends with haploid cells

mitosis happens daily in each dividing cell and starts with diploid cells and ends with diploid cells

which process creates identical daughter cells and how many are created?

mitosis: two

which process creates unique daughter cells, and how many are created?

meiosis: four

what is a chromosome

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

What are homologous chromosomes?

paired chromosomes with genes for the same traits arranged in the same order

What is a haploid cell? What process is it found in?

a cell that contains one set of chromosomes: Meiosis

What is a diploid cell? What process is it found in?

A cell with two sets of chromosomes: mitosis

How many pairs of homologous chromosomes do humans have

22 pairs

How many total chromosomes do humans have?

46

When do homologous chromosomes separate?

Meiosis I

What are sister chromatids?

structures that contain identical copies of DNA

When do sister chromatids separate?

anaphase II

What is a gene?

A section of DNA on a chromosome that codes for a particular trait

Where are genes found?

in DNA

Allele

one variant of a particular gene

What is a dominant allele?

the trait which is preferentially expressed in an organism over alternative forms of the trait

What is a recessive allele?

A trait that must be present on both homozygous chromosomes in order to be expressed in an organism. (lower case letter)

Homozygous

a genotype having two identical alleles of a particular gene

Heterozygous

A genotype that has two different alleles for a trait

what is a genotype

the genetic constitution of an individual organism or of a single pair of alleles

What is a phenotype?

physical characteristics

Is it easier to tell the genotype of an individual with a dominant or recessive phenotype

recessive because they can only have one genotype whereas a dominate gene carrier can be heterozygous or homozygous

What is a Punnet Square?

a diagram that is used to predict an outcome of a particular cross or breeding experiment

Can you identify dominate and recessive alleles when given a Punnet Square

yes

can you determine the possibility of getting a certain phenotype or genotype from a punnet square

yeh

What is a monohybrid cross?

a cross that involves hybrids for a single trait

What ratio of phenotypes would you expect from a monohybrid cross

if they are both heterozygous, it's 2;1

how can I tell if my cats are heterozygous

if you bred them together and 25% of the kittens display a recesive trait

What types of kittens can I expect from breeding two non dilute cats?

solid colored kittens and possibly a small amount of dilute colored kittens

What types of kittens can I expect from breeding two dilute cats?

dilute kittens only

Is it easier to obtain pure-breeding non-dilute (dominant allele) or dilute (recessive allele) cats?

Dilute

What is a dyhybrid cross?

mating between two individuals that are heterozygous for 2 different genes. ex) Rr and Gg

How many alleles are involved in a dihybrid cross?

four

What does independent assortment mean?

The alleles do not influence each other in regards to which goes on to be in a gamete. Each allele has an equal probability of going inside a gamete (regardless to whether it is dominant or recessive).

This means that, for two genes with two alleles each (alleles A/a and B/b), there are four possible combinations you might see in a gamete--AB, Ab, aB and ab

Mendel assumed that these allele combinations will appear equally often in the individual's gametes

How many genotypes in a dihybrid cross

nine

what ration of phenotypes do we expect to see in a dihybrid cross?

9:3:3:1

What are pedigrees used for

To make predictions about future offsprings.

autosomal

all the other genes in the body that are not sex-linked.

What is a carrier

heterozygous genotype that carries recessive trait but doesn't express it

who is more likely to be a carrier

women

What kind of genetic counseling would you provide to a hemophilic father who learned his wife was about to give birth to a son?

he will not pass the disease on because it is carried on the x chromosome and he will be giving the son a y chromosome

What does incomplete dominance mean?

when the phenotype of the two alleles blend

what does polygenic inheritance mean

when two or more genes affect a single character

Do we see any recessive traits more often than expected

not having a widow's peak

can you have dominate alleles for disease states

ya