W1 Classic Mendelian Genetics 1

Question 1

Who is Gregor Mendel?

Answer 1

An Austrian who experimented with pea plants and correctly argued that parents pass on heritable factors - mendelian genetics

Question 2

what is a character?

Answer 2

a heritable factor that varies between individuals (seed colour, seed shape, flower colour)

Question 3

what is a trait?

Answer 3

the variations within a character (yellow or green seeds, round or wrinkled shape)

Question 4

what is true-breeding?

Answer 4

self-fertilisation producing identical offspring to the parent (true-breeding parents = P generation)

Question 5

what is a hybrid?

Answer 5

offspring of two different varieties ( called the F1 generation)

Question 6

what is a cross?

Answer 6

fertilisation between two different individuals, between two F1 individuals (producing an F2 generation)

Question 7

what is a heritable factor now known as?

Answer 7

a gene

Question 8

what is the unit of genetic inheritance?

Answer 8

alleles, you get one allele from each parent which can be the same or different (homozygous = same, heterozygous = different)

Question 9

what is the difference between a dominant and recessive allele?

Answer 9

a dominant is always expressed, a recessive is not expressed unless there is no dominant allele present

Question 10

what is the idea/law of segregation?

Answer 10

alleles are separated/segregated randomly during gamete formation

Question 11

what is independent assortment?

Answer 11

segregating pairs of alleles assort independently of each other

Question 12

what are Mendels four postulates of genetics?

Answer 12

1 - unit of genetic inheritance
2 - dominance/recessiveness
3 - segregation
4 - independent assortment

Question 13

What is an allele?

Answer 13

an alternative version of genes that account for variations in inherited characters

Question 14

what is a gene?

Answer 14

a DNA segment that contains the regulatory and coding sequences for expression of the gene product

Question 15

what does a gene encode?

Answer 15

an RNA transcript (may have its own biological activity)

Question 16

what does a gene reside?

Answer 16

at a specific locus on a specific chromosome

Question 17

what is a ‘wildtype’?

Answer 17

the more common allele / major allele (less common one is called minor allele)

Question 18

how many alleles does an individual inherit from each parent for each character?

Answer 18

only one allele

Question 19

if two alleles at a particular locus are identical what is this due to?

Answer 19

true-breeding from the P generation

Question 20

if the alleles are different how many traits are visible?

Answer 20

only one

Question 21

which type of allele determines phenotype?

Answer 21

the dominant allele

Question 22

at what stage do the two alleles for a gene separate?

Answer 22

during gamete formation (end up in different gametes)

Question 23

what does the segregation of alleles correspond to?

Answer 23

the distribution of homologous chromosomes to different gametes in meiosis

Question 24

all cells except gametes have homologous pairs of chromosomes so they are diploid or haploid?

Answer 24

diploid

Question 25

gametes have only a single copy of each chromosome so they are diploid or haploid?

Answer 25

haploid

Question 26

at what stage of meiosis does recombination (crossing over) take place between homologous chromosomes?

Answer 26

during prophase 1 of meiosis

Question 27

are alleles that are closer together or further apart more likely to become separated during crossing over?

Answer 27

ones that are further apart are more likely to separate

Question 28

after crossing over are the homologous chromosomes separated into different or the same combinations in the gametes?

Answer 28

different

Question 29

what is the definition of heritabilty (H2)?

Answer 29

the proportion of the variation in a population that is attributable to genetic differences

Question 30

what is the calculation for heritabilty (H2)?

Answer 30

genetic variance / (genetic variance + phenotypic variance)

Question 31

what is selective breeding?

Answer 31

only using males and females for breeding that have passed a certain quality criteria

Question 32

what is the goal of selective breeding?

Answer 32

to genetically improve the heritable qualities of a population in a certain direction e.g. more muscle, higher milk yield

Question 33

what is genotype?

Answer 33

the assortments of alleles an individual has (complete heritable genetic identity)

Question 34

what is a phenotype?

Answer 34

the physical expression of the genes an individual has

Question 35

what is complete dominance?

Answer 35

when phenotypes of the heterozygote and dominant homozygote are identical

Question 36

what is incomplete dominance?

Answer 36

when the phenotype of F1 hybrids is somewhere between the two parents varieties (an intermediate phenotype)

Question 37

what is codominance?

Answer 37

when two dominant alleles affect the phenotype in separate distinguishable ways

Question 38

what is pleiotropy?

Answer 38

genes that have multiple but unrelated (e.g. colour and eye shape) phenotypic effects

Question 39

what is epistasis?

Answer 39

when a gene at one locus influences the phenotypic expression of a gene at a second locus (e.g. coat colour is determined by two genes)