Genes and Inheritance lectures Flashcards

1
Q

gene

A

unit of heredity, carrying information for a single polypeptide or RNA

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2
Q

gamete

A

a mature reproductive cell

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3
Q

allele

A

a variant of a genetic character at a given locus on a chromosome

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4
Q

Mendel’s rule of independent assortment

A

alleles of different genes assort independently

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5
Q

monotypic nature of the phenotype

A

controlled by two alleles (dominant and recessive)

only one ‘visible’

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6
Q

dihybrid

A

cross with two genes

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7
Q

recombinant phenotypes

A

different from either parent

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8
Q

recombination through meiosis

A

whole chromatids

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9
Q

crossing over of chromatids

A

part of chromatid

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10
Q

what does recombination frequency tell us?

A

how far apart the genes are

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11
Q

what is recombination frequency measured in?

A

cM (centiMorgans) or genetic map units

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12
Q

how many base pairs of DNA is 1cM?

A

1,000,000

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13
Q

recombination frequency

A

((number of recombinants)/(total number of progeny))

X 100

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14
Q

haplotype

A

a group of genes inherited together from a single parent

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15
Q

Labradors’ example

what are the names of the proteins for black and brown fur?

A
DHI-melanin = dark brown-black
DHICA-melanin = brown
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16
Q

Labradors’ example

what does Tyrosinase-related protein 1 do?

A

participates in conversion of a darker eumelanin (black) to lighter (brown)

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17
Q

Labradors’ example

what colour of fur do homozygous carriers of mutant Trp1 turn?

A

brown

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18
Q

Which gene codes for Tyrosinase-related protein 1?

A

Trp1 (Tryp) gene

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19
Q

What is the Labrador’s example about?

A

Fur colour

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20
Q

What is Agouti?

A

A specific colouring of fur?

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21
Q

Is the allele for Agouti in the Agouti mouse dominant or recessive?

A

dominant

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22
Q

How does Agouti fur come about?

A

by introducing a band of yellow colour resulting from deposition of phaeomelanin (yellow pigment) on dark hair)

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23
Q

What does loss of function of the Tyr gene cause?

A

no melanin -> albino

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24
Q

what pattern results if there are no melanocytes present in certain areas?

A

spotting pattern

Kit gene

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25
Q

what can multiple alleles lead to?

A

a hierachy of dominance

26
Q

Rabbit example

Order the coats in dominance over each other.

A

Sable Chinchilla Iron grey Himalayan White

27
Q

What is incomplete dominance?

A

many alleles not completely dominant or recessive - their effects blend together or mix

28
Q

what is an example of incomplete dominance?

A

colours of snap-dragon flowers

29
Q

Does incomplete inheritance still follow Mendel’s laws?

A

yes

30
Q

What is co-dominance?

A

the effects of both alleles can be seen together in the phenotype.

31
Q

what is an example of co-dominance?

A

Human ABO blood group system

32
Q

What is epistasis?

A

The expression of one gene can be conditional on the allele of another gene.

33
Q

What is an example of epistasis?

A

Labrador coat colour

34
Q

How is labrador coat colour an example of epistasis?

A

Gene B involves pigment production
Gene E involves pigment deposition (E would mean pigment deposited)

Allele of gene B matters only if allele E of the other gene is present

35
Q

What is an example of a gene-environment interaction?

A

Siamese cats

36
Q

What is a gene-environment interaction?

A

many genes influence the phenotype in a way modified by the environment.

37
Q

What is the penetrance?

A

The proportion of individuals carrying the allele that actually show the phenotype

38
Q

Polygenic Inheritance

A

many traits are influences by several genes together (polygenes)

39
Q

What are examples of polygenic traits?

A

Humans - height, skin colour…

40
Q

What type of data are the traits of human height and skin colour?

A

continuos

41
Q

What is the analysis of traits followed in families?

A

pedigree analysis

42
Q

what are examples of pedigree analysis?

A

some human diseases

haemophilia

43
Q

Autosomal dominant inheritance

A

every individual has an affected parent
both sexes affected
~50% of the offspring are affected

44
Q

Autosomal recessive inheritance

A

Both parents not affected
~25% of the offspring affected
Phenotype occurs in both sexes

45
Q

monoecious

A

individuals can produce both male and female gametes

46
Q

dioecious

A

individuals are either male or female

47
Q

XO, XY, ZW

what does this show evidence of?

A

Sex determination has evolved independently many times

48
Q

Bee example

unfertilised eggs

A

haploid -> produce males (drones)

49
Q

Bee example

fertilised eggs

A

diploid -> produce females (workers/queen)

50
Q

Bee example

do bees have sex chromosomes?

A

No

51
Q

Bee example

how is sex of offspring determined in bees?

A

Females are heterozygous for complementary sex determiner gene (CSD)

52
Q

Bee example

how many different CSD genes are there?

A

19

53
Q

Bee example

what are infertile males and what happens to them?

A

homozygous for CSD genes (rare)

killed by workers

54
Q

What do the genes SRY and DAX1 do in humans?

A

SRY - promotes testis development

DAX1 - prevents testis development and allow ovary development

55
Q

Where are the SRY and DAX1 genes located on humans?

A

SRY - Y chromosome

DAX1 - X chromosome

56
Q

Where are sex-linked genes found?

A

On the X chromosome

57
Q

What is non-nuclear inheritance

A

Mitochondrial and plasmids

58
Q

Genes in mitochondrial DNA

A

13 coding genes

37 genes in total

59
Q

Mitochondrial diseases - offspring sex affect

A

Females - all offspring affected

Males - no offspring affected

60
Q

Drosophila

Sex chromosomes

A

XO sterile male
XXY female

opposite way to in mammals
XY female
XX male