D3.2 Inheritance

Question 1

describe Gregor Mendel’s experiment and his findings

Answer 1

1. placed homozygous dominant male pollen into recessive female ovaries of pea plants
2. F1 generation 100% heterozygous
3. F2 generation 1:2:1 (homozygous dominant:heterozygous:recessive), 3:1 (dominant:recessive)

Question 2

when did Mendel conduct his pea experiment, and what did he first call genes?

Answer 2

1865; factors

Question 3

allele

Answer 3

version of gene; codes same trait but different variations

Question 4

heterozygote

Answer 4

organism with 1 dominant, 1 recessive allele of a gene

Question 5

homozygote

Answer 5

organism with either 2 dominant or 2 recessive alleles of a gene

Question 6

monohybrid cross

Answer 6

cross between two parents focusing on just 1 trait (eg Tt×TT, ff×FF, Gg×Gg, etc)

Question 7

draw two Punnett grids representing Mendel’s experiment findings

Answer 7

1. TT×tt = Tt, Tt, Tt, Tt
2. Tt×Tt = TT, Tt, Tt, tt

Question 8

what is a carrier of a gene?

Answer 8

heterozygous organism having recessive allele that doesn’t affect its phenotype

Question 9

examples of phenotypical characteristics exclusively due to genetics

Answer 9

ABO blood, Huntington’s, colour blindness, cystic fibrosis

Question 10

examples of phenotypical characteristics exclusively due to envrionment

Answer 10

learning math and songs, scars, large muscles

Question 11

examples of phenotypical characteristics due to both genetics and environment

Answer 11

height, cancer

Question 12

codominant alleles

Answer 12

when heterozygote has two alleles that are dominant and both phenotypes are expressed (eg having both IA and IB alleles results in AB blood type)

Question 13

incomplete dominance

Answer 13

when heterozygote has two alleles that are dominant and neither phenotype is expressed, only a mix (eg mixing pure-bred white and red four o’clock flowers results in pink flowers)

Question 14

phenotypic plasticity

Answer 14

ability to express phenotype differently based on environment (adaptation)

Question 15

phenological events

Answer 15

phenological changes based on changes in environment during cyclical events (like seasonal food availability)

Question 16

how does freshwater snail physa virgata employ phenoplastic plasticity?

Answer 16

shell normally conical and elongated, different genes expressed to become rounded when predator around so harder to crush

Question 17

phenylketonuria

Answer 17

autosomal disease from PAH gene mutation, resulting in decreased production of phenylalanine hydroxylase, which converts toxic phenylalanine from proteins to tyrosine

Question 18

examples of autosomal recessive diseases

Answer 18

albinism, cystic fibrosis, sickle cell disease, Tay Sachs, thalassemia

Question 19

how do humans taste bitterness?

Answer 19

1. if one has TAS2R38 gene that codes for taste receptor 2 member 38, phenylthiocarbamide can attach to receptor, allowing taste bitterness
2. single-nucleotide polymorphisms make alleles of TAS2R38 gene, which don’t code for receptor

Question 20

how many alleles, genotypes, and phenotypes contribute to ABO blood type?

Answer 20

3 alleles, 6 genotypes, 4 phenotypes

Question 21

what are the two types of chromosomes?

Answer 21

22 autosomes, 1 pair allosomes (sex chromosomes)

Question 22

differences between X and Y chromosomes

Answer 22

1. X codes for oestradiol and progesterone production, Y for testosterone
2. Y 70 genes vs X 800, most genes on X no allele on Y to pair with

Question 23

what determines sex in humans?

Answer 23

XX = female, XY = male; sperm determine gender (50% sperm have Y, 50% X)

Question 24

sex-linked trait

Answer 24

genetic trait with gene locus on X (rarely Y) chromosome; often affects males more

Question 25

haemophilia

Answer 25

sex-linked recessive trait caused by allele on X chromosome causing trouble blood clotting

Question 26

what kind of trait is huntington’s

Answer 26

autosomal dominant trait

Question 27

draw a pedigree chart of the P and F1 generations of a female without huntington’s and a male heterozygous for it

Answer 27

hh × Hh = hh, Hh, Hh, hh

Question 28

what effect does incest have on genetic diseases?

Answer 28

increases frequency of rare diseases (eg families with Huntington’s are 50% affected while general population only 0.01%)

Question 29

polygenic inheritance

Answer 29

when multiple genes influence expression of 1 trait, increasing possible genotypes and allowing continuous variation

Question 30

continuous variation

Answer 30

when continuous array of phenotypes possible because of polygenic inheritence (eg intensity of skin colour controlled by at least 4 genes controlling melanin production)

Question 31

discrete variation

Answer 31

when only 1 gene responsible for trait, allowing discrete phenotype options; can be shown on bar graph

Question 32

dihybrid cross

Answer 32

cross between two parents focusing on 2 traits (eg RrYy×RrYy, RRYY×rryy, etc)

Question 33

mendelian ratios for dihybrid cross results

Answer 33

• 9:3:3:1 for 2 parents heterozygous for both traits
• 1:1:1:1 for 1 parent heterozygous for both traits, 1 parent recessive for both traits (test cross)

Question 34

what were mendel’s two laws?

Answer 34

• law of segregation: each gamete only receives 1/2 copies from each parent (meiosis)
• law of independent assortment: each chromosome is inherited independent of each other, unless on same chromosome/too close to be shuffled in crossing over (recombination rate under 50%)

Question 35

linked genes

Answer 35

on same chromosome/close together, usually passed down together; changes predicted ratios of dihybrid crosses

Question 36

what is a group of linked genes called?

Answer 36

linkage group

Question 37

draw possible offspring genotypes for a fruit fly heterozygous for brown body and normal wings, and another homozygous for black body and vestigial wings (with crossing over)

Answer 37

BbVv×bbvv = BbvV×bbvv = Bbvv and bbVv