Mendelian Inheritance - Week 2

Question 1

who came up with the pea plant experiment

Answer 1

gregor mendel

Question 2

what did gregor mendal know nothing about

Answer 2

• dna
• chromosomes
• meiosis

Question 3

what is the gene

Answer 3

the basic unit of inheritance

Question 4

what are genes

Answer 4

genes are segments of DNA and genes are short sections of chromosome

Question 5

How do chromosomes come

Answer 5

as a pair
- one from sire
- one from dam

Question 6

how many pairs of chromosomes do :
pigs:
humans:
sheep:
cattle/ goats
horse:
dogs/ chickens:

Answer 6

pigs: 19
humans: 23
sheep: 27
cattle/ goats: 30
horse: 32
dogs/ chickens: 39

Question 7

what is an allele

Answer 7

any one of the alternative forms of a specified gene
e.g black, brown and red hair

Question 8

define Dominance:

Answer 8

one member of an allelic pair is manifested to the exclusion of the other

Question 9

define recessive

Answer 9

one member of an allelic pair lacking the ability to manifest itself when the dominant member is present.

Question 10

what is Mendel’s 2nd law

Answer 10

independent assortment

Question 11

what happens during gamete formation

Answer 11

segregating pairs of genes assort independently of each other

Question 12

why do genes on the same chromosome tend to end up in the same gamete

Answer 12

due to crossing over

Question 12

what does mendels law of segregation state

Answer 12

at species procreation the paired chromosomes split. The chromosomes segregate into the gametes independently of each other

Question 12

define Genetic Linkage

Answer 12

some alleles on a specific chromosome tend to stay together.

Question 13

what is crossing over?

Answer 13

exchange of chromosome segments causing genes to recombine

Question 13

what happens to genes that are closer to the centromere

Answer 13

the less they take part in recombination

Question 14

what is recombination frequency a measure of

Answer 14

a measure of the linear distance between genes.
-it allows genes to be mapped

Question 15

what is the unit of a distance

Answer 15

a centimorgan
(recombinant frequency per 1/100 gametes)

Question 16

what is the ratio of mendelian trait

Answer 16

3:1
Punnett Square

Question 17

who came up with Dihybrid cross

Answer 17

Gregor mendel

Question 18

what is a dihybrid cross

Answer 18

cross with two pairs of contrasting traits

example:
- green v yellow
- wrinkled v round

Question 19

what is Dominance

Answer 19

is the interaction of genes at a locus so that in a heterozygote one allele has more effect than the other

-the allele with the greater effect is dominant over its recessive.

Question 20

what is complete dominance

Answer 20

the expression of the heterozygote is identical to the expression of the homozygous dominant genotype

Question 21

what is heterozygote

Answer 21

they have two forms of alleles
e.g Yy

Question 22

what is partial dominance

Answer 22

the expression of the heterozygote is intermediate to the expression of the homozygous dominant genotype and more closely resembles the homozygous dominant genotype

Question 23

what is no dominance

Answer 23

the expression of the heterozygote is exactly midway to the expression of the homozygous genotypes

Question 24

what is over dominance

Answer 24

the expression of the heterozygote is outside the range defined by the homozygous genotypes and most closely resembles the expression of the homozygous dominant genotype.

Question 25

what gene is horses is partially dominant but cannot be considered good

Answer 25

HYPP

Question 26

what are the two genes that affect dog coat colour

Answer 26

E gene
- melanocyte stimulating hormone Receptor Gene (MSHr)

B gene
- Tyrosinase Related Protein 1

Question 27

what does MSHr mean

Answer 27

Melanocyte Stimulating Hormone Receptor Gene
-E gene in dog

Question 28

what is an epistatic gene

Answer 28

an interaction of genes at different loci such that the expression of genes at one loci depends on alleles present at other loci

Question 29

what is the “product law “ of probabilities

Answer 29

When two independent events occur simultaneously, their combined probability is equal to the product of their individual probabilities of occurrence.

Question 30

name the 3 sex related inheritance

Answer 30

1. sex linked
2. sex limited
3. sex influenced

Question 31

what is sex linked?

Answer 31

pattern of inheritance is located on the sex chromosomes (x & y)

• females carries two X chromosomes
• males have one X (dam) and one Y (sire) chromosome

Question 32

what is sex limited

Answer 32

phenotypic expression is linked to one sex
- milk yields in cows only

Question 33

what is sex influenced

Answer 33

modes of gene expression is different between males and females
- dominant in one sex and recessive in another

Question 34

example of sex influenced inheritance

Answer 34

-Scurs (small, movable horn-like growths)
– Allele for scurs is dominant in males and recessive
in females
– Male only needs one copy to have scurs
– Female requires two copies

Question 35

what is Mendelian sampling

Answer 35

-The random sampling of parental genes caused by segregation and independent assortment of genes during germ cell formation and by random selection of gametes in the formation of the embryo.

Question 36

how does mendelian sampling create a problem for animal breeders

Answer 36

• creates problems for Animal breeders as it makes it difficult to predict the outcome of mating

Question 37

define zygote

Answer 37

a cell formed from the union of male and female gametes.
-has full compliment of genes