test 2

Question 1

big exception to mendel’s ideas

Answer 1

chromosome theory and linkage

Question 2

sutton/boveri chromosome theory

Answer 2

genes are located on chromosomes

• genes (alleles) and chromosomes both occur in pairs
• allele pairs and chromosome pairs both separate from each other and enter separate gametes
• separation of both allele pairs and chromosome pairs are independent

Question 3

proof of chromosome theory

Answer 3

morgan created research group called Drosophila group

group showed that certain gene was on the X chromosome and therefore the chromosome theory must be true

Question 4

morgan’s observations

Answer 4

strange results from cross between white-eyed female and red-eyed male (all red-eyed females and all white-eyed males)
could only explain strange results if he assumed the white-eyed gene was on the X chromosome

Question 5

bridge’s final proof of chromosome theory

Answer 5

experiment with nondisjunction where he produced XXY female
in various sex chromosomes that resulted from these females, the X chromosome and the white eye gene seemed to be transmitted together
proof was first article in first volume of journal Genetics

Question 6

X linkage in humans

Answer 6

genes on X chromosome=X linked

ex: hemophilia A and red green color blindness

Question 7

sex linked genes

Answer 7

gene on X or Y chromosome

Question 8

how many PARs on X and Y chromosomes

Answer 8

2 PARs

at tip of each telomere

Question 9

linkage

Answer 9

more than 1 gene is located on each chromosome so 2 genes found on the same homologous pair of a chromosome will not obey mendel’s law of independent assortment
alleles will move together (linked)
for a 2 point cross there are 2 possibilities

Question 10

parental and recombinant gametes

Answer 10

gametes F1 individual makes are either:

• same combo of alleles as P generation
• opposite combo of alleles as P generation

Question 11

independent assortment vs. linkage

Answer 11

if genes are on different chromosome pairs they will assort independently (# of P gametes will be ~equal to # of recombinant gametes)
if 2 genes are on same chromosome pair they will not assort independently but will be linked (# of P gametes will be significantly greater than # of recombinant gametes)

Question 12

recombinant gametes and crossing over

Answer 12

for linked genes recombinant gametes are produced by crossing over between 2 genes
even if crossover occurs the products of a single meiotic event will be 2 parental and 2 recombinant alleles

Question 13

predicting outcome of dihybrid cross involving linked genes

Answer 13

punnet square using probabilities
list gamete genotypes and probability of each gamete (probability calculated if you know distance between genes)
probabilities of each gamete pair multiplied together giving frequency of each genotype

Question 14

gene mapping

Answer 14

for linked genes the distance between is proportional to the frequency of crossing over
further apart 2 genes are the more likely a crossover will occur between them
ex: 1% recombinant gametes=1 map unit or cM
max distance=50 cM

Question 15

3 point test cross

Answer 15

used bc 2 point test crosses often overlook double crossovers
individual crossed with homozygous recessive
analysis reveals gene order, distance between genes, and the degree of interference

Question 16

steps of 3 point cross

Answer 16

1. determine gene order
2. determine distance between genes
3. calculate coefficient of coincidence

Question 17

what is the coefficient of coincidence

Answer 17

decimal that expresses what proportion of expected double crossovers actually happened

Question 18

mapping in organisms with an ordered tetrad

Answer 18

ascomycetes (all products of single meiosis in sac)
some have cells maintained in order in which they are produced by meiosis I and II (possible to map distance between gene and its centromere)
4 of 1 kind on top and 4 of other kind on bottom

Question 19

somatic cell hybridization

Answer 19

technique used in 1960s to map some human genes to chromosomes or even regions of a chromosome
fusion of human tissue culture cell to mouse cell
human cells preferentially lost so you can get cell with all mouse chromosomes but 1 human chromosome so if cell still produces specific human product then gene for that product must be on that chromosome

Question 20

FISH

Answer 20

fluorescent in situ hybridization

technique involves hybridizing a probe DNA molecule (tagged with fluorescent marker) to a spread of chromosomes

Question 21

SNPs and GWASs

Answer 21

single nucleotide polymorphisms and genome-wide associated studies
use common variants of a single DNA base pair as markers to hunt for genes related to a trait or disease

Question 22

LOD score

Answer 22

log of odds favoring linkage
used in population genetics
pedigree analysis can be used to infer linkage of 2 genes
estimate probability that pedigree was produced by 2 genes linked at a given distance vs. produced by 2 non linked genes

Question 23

discovery of nucleic acids

Answer 23

miescher
isolated new substance from nuclei of cells (“nuclein”) which he realized was new class of organic material
knew it wasn’t protein bc it had no S but had P
nuclein was probably mixture of DNA and RNA
“nucleic acids” today

Question 24

DNA as genetic material of almost everything

Answer 24

avery, macleod, and mccarty
showed DNA was genetic material of bacterium that causes type of pneumonia in mice
based on griffith experiment with bacteria with/without capsule (S and R) (“transforming principle”)

Question 25

RNA as genetic material of some viruses

Answer 25

some viruses have no DNA but do have RNA some RNA viruses replicate their RNA using RNA replicase or enzyme reverse transcriptase to make DNA intermediate which is then copied to RNA viruses called "retroviruses"

Question 26

DNA structure

Answer 26

polynucleotide (polymer of nucleotides)

Question 27

DNA polynucleotide

Answer 27

polynucleotide made by joining many nucleotides together 3' pentose sugar bonded to 5' phosphate of next nucleotide DNA has sugar-phosphate backbone with bases protruding off 1 side

Question 28

nucleotide

Answer 28

each DNA (or RNA) nucleotide is composed of 3 subunits (phosphate, pentose, base)

Question 29

nucleoside

Answer 29

pentose and base (no phosphate)

Question 30

purines

Answer 30

have a double ring structure and are larger than pyrimidines | adenine and guanine

Question 31

pyridines

Answer 31

single ring structure and are smaller than purines | cytosine and thymine (uracil replaces thymine in RNA)

Question 32

the double helix

Answer 32

watson and crick proposed 3-D model for structure of DNA (double helix) work based on x-ray crystallography work of Franklin and Wilkins and work of chargaff (A=T and G=C) and general understanding of structure of DNA polynucleotide

Question 33

strands of DNA

Answer 33

2 antiparallel nucleotide strands running in opposite polarity

Question 34

alpha helix

Answer 34

the 2 strands are coiled in an alpha helix (right handed helix)

Question 35

specific base pairing

Answer 35

A always paris with T and G always pairs with C base pairing is by hydrogen bonding involving N, O, and H 3 bonds that hold G to C 2 bonds that hold A to T

Question 36

dimensions of the double helix

Answer 36

3.4 A thick and stacked internally with of molecule is 20 A and makes 1 complete turn ever 34 A 10 base pairs per turn of the helix

Question 37

eukaryotes--the unineme theory of histones

Answer 37

prokaryotic chromosome is 1 circular DNA molecule eukaryotic chromosome DNA is linear each chromosome has 1 long DNA molecule (unineme theory) wound around clusters of 8 histones