ch 5: variation among individuals

Question 1

the only way a new allele can occur in a species is through…

Answer 1

mutation

Question 2

there are three ways of getting new combinations; they are…

Answer 2

• fertilization (which egg and which sperm)
• independent assortment (not every gamete is an exact copy of it’s mother cell)
• crossing over (chromosomes pair up and switch loci)

Question 3

purines have ___ ring(s)

Answer 3

2

Question 4

pyrimidines have ___ ring(s)

Answer 4

1

Question 5

cytosine and thymine (and uracil) are…

Answer 5

pyrimidines

Question 6

adenine and guanine are…

Answer 6

purines

Question 7

phosphodiester bond

Answer 7

a chemical bond that forms between one sugar molecule to another; from 3’ to 5’ (think: sugar phosphate backbone)

Question 8

how is RNA different than DNA

Answer 8

• single chain
• have a ribose (not a deoxyribose) group
• has uracil instead of thyamine

Question 9

point mutation

Answer 9

when a single nucleotide base is changed, inserted, or deleted from a DNA or RNA sequence

Question 10

substitution

Answer 10

when a single nucleotide is swapped for another single nucleotide (replaces it)

Question 11

silent substitution

Answer 11

when a substitution does not affect the final amino acid that is created (3rd position is usually safe)

Question 12

replacement substitution

Answer 12

when a substitution does affect the final amino acid that is created (usually 1st or 2nd position)

Question 13

why are third position substitutions usually fine

Answer 13

most codons for certain amino acids have four variants; only varying in the final slot, so usually a third position substitution does not change the final amino acid

Question 14

how does sickle cell anemia work

Answer 14

if one codon is messed up in a 143 amino acid-long chain, sickle cells are made; they block capillaries since they can’t fit through single file

Question 15

transition

Answer 15

when the nucleotide that is swapped is the same type; purine for purine or pyrimidine for pyrimidine
- 60% more likely to stick around than a transversion

Question 16

transversion

Answer 16

when the nucleotide that is swapped is a different type; purine for pyrimidine or pyrimidine for purine
- rare due to how disruptive they are

Question 17

indel

Answer 17

the term for an “insertion or a deletion” when looking at mutations

Question 18

deleterious

Answer 18

causing harm or damage; used often in biology

Question 19

explain the C. elegans fitness experiment

Answer 19

control group: had competition, similar to the natural environment
test group: had a “perfect environment” where the survival rate plummeted as generations passed (natural selection and mutation go hand in hand)

Question 20

explain the significance of dna polymerase in mutation

Answer 20

• it makes 1 error in every 100,000,000 bases
• has “faster polymerases” and “slower polymerases”
• fast lineages are faster walkers and unbinders
• we see fast lineages do well in novel environments, have more frequent mutations, and do better on islands (island species have fast lineages

Question 21

missense mutation

Answer 21

a change from one amino acid to another; and it changes the codon (could be harmless)

Question 22

nonsense mutation

Answer 22

a change from an amino acid to a “stop” codon (UAA, UAG, and UGA)

Question 23

what is the start codon

Answer 23

AUG

Question 24

neutral mutation

Answer 24

a change from an amino acid to another amino acid w/ similar chemical properties

Question 25

silent mutation

Answer 25

a change of a codon where the same amino acid ends up being specified

Question 26

frameshift mutation

Answer 26

the addition or deletion of one or a few base pairs leads to a change in reading frame

Question 27

reverse transcription

Answer 27

when DNA is made from RNA; processed mRNA is reinserted into a new locus of a chromosome
- this can happen during prophase 1 of meiosis i

Question 28

fetal hemoglobin

Answer 28

fetal hemoglobin takes priority over maternal hemoglobin, so the fetus is more prone to stripping O2 from the bloodstream.

Question 29

paralogs

Answer 29

one of a set of homologous genes that have diverged from each other as a consequence of genetic duplication

Question 30

orthologs

Answer 30

genes in different species that evolved from a common ancestral gene by speciation

Question 31

linkage groups

Answer 31

areas/loci on a chromosome that are closer together and therefore less likely to be separated during crossing over

Question 32

inversions

Answer 32

when a section of a chromosome detaches, reverses, and reattaches - does not match/line up well
- now, the gene packet will always travel together; new bonds/zippering is extra reinforced

Question 33

polyploidy

Answer 33

having diploid zygotes (errors can occur during meiosis i & ii)
- happens often with plants bc many self-fertilize

Question 34

what does polyploidy allow

Answer 34

since an organism will have a spare genome; one remains static and the other is free to drift and mutate w/o causing harm to the organism

Question 35

examples of plants with polyploidy

Answer 35

• cotton, coffee, bananas, sugarcane
• 95% of fern species are polyploid
• THERE’S EVEN A RAT SPECIES

Question 36

AIDS resistance

Answer 36

having a faulty CCR5 protein is advantageous because it doesn’t let the virus into the white blood cell (leading to an impaired immune system, but no AIDS)

Question 37

genotypes and AIDS resistance

Answer 37

+/+ = normal (403 bp and 332 bp)
change32/change32 = (371 bp and 332 bp)
+/change32 = (332 bp, 371 bp, and 403 bp)

Question 38

CCR5

Answer 38

a cell surface protein that, if tampered with, doesn’t let the AIDS virus into the white blood cell (you will have an impacted immune system, but no AIDS).