Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Genetics > M2 L8 Sex Determination and Sex Chromosomes > Flashcards

M2 L8 Sex Determination and Sex Chromosomes Flashcards

(check video for card 19)

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

homomorphic chrom

A

chrom whose meiotic partner has the same length and content (usually autosomes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

heteromorphic chrom

A

chrom whose meiotic partner has dif length and content (usually sex chrom)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

sex chrom

A

chrom whose presense, absence, or quantity play a role in sex determination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

primary sex det

A

gonad differences between sexes (ovaries and eggs or testes and sperm)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

secondary sexual differentiation

A

morphological differences between sexes not involving the gonads (ex. color, vocalizations)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

heterogametic sex

A

the sex that does not make gametes with identical sex chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

dioecious (gonochoric)

A

species that have two distinct sexes or individuals with either M or F gonads

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

homogametic sex

A

sex that makes gametes with identical sex chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

monoecious (hermaphroditic)

A

individuals w/ both M and F gonads and produce functional eggs and sperm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

intersex

A

only refers to individuals of a dioecious species that have an intermediate gonad phenotype (ovotesties) – often sterile

some species of moles have F w/ ovotesties –> testosterone but no functional sperm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are chalmydomonas

A

unicellular green algae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how do chlamydomonas reproduce in permissive conditions

A

haploid asexual reproduction via mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how do chlamydomonas reproduce in stressful conditions

A

+ cells make + gametes, - cells make - gametes (isogamous)

+ and - gametes unite –> zygote resistant to stress

favorable conditions –> zygote does meiosis –> 4 vegetative asexual reproducing haploid cells (2+ and 2-)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what leads to sexual differentiation in chamydomonas

A

different alleles at the mt locus (+ or -)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

is maize monoecious or dioecious?

A

individual flowers are dioecious but each maize plant can have M and F flowers –> each plant is monoecious

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is maize monoecious with dioecious flowers? What effect do mutations have?

A

maize flowers have genes to selectively abort M or F flowers –> flowers are dioecious (M or F) but different flowers within the same plant selectively abort different sex structures (some might abort M, others abort F)

mutations in genes for aborting M/F structures can lead a maize plant to make all M or all F flowers –> plant is dioecious

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how is sex determined in c. elegans (roundworms)? What’s the evidence? What are the karyotypes?

A

XO sex determination

ratio of X chrom to autosomes (1:2 X:autosome = male, 1:1 = hermaphrodite, 3:2 = smaller hermaphrodite, 2:1 = nonviable)

most common: 2X, 2N –> 1:1 ratio X:autosomes –> hermaphrotites

X:2N –> 1:2 ratio X:autosomes –> male (from nondisjunction in F meiosis I of II)

XX:4N –> male –> 2X does not = hermaphroditic

XXX:2N –> smaller, less fertile hermaphrodites

XXXX:2N –> nonviable embryo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how is sex determined in drosophila?

A

XY sex determination

determined by ratio X:autosome

XY = male, XX = female

XXY = F –> presence of Y does not cause M and absence of Y does not cause F

XO = sterile M –> Y chrom vital for M fertility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what do triploid F drosophila show?

A

ratio X:autosomes determines sex (3X:3A –> female)

triploid F viable and some fertile

come from 2N egg (from nondisjunction) and N sperm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the key ratios and phenotypes in drosophila

A

greater than 1:1 X:autosome –> would be F if viable (metaF)

1:1 X:autosome –> F

between 1:2 X:autosome –> Intersex

1:2 X:autosome –> M

less than 1:2 X:autosome –> would be M if viable (metaM)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what’s the transformer gene in drosophila? who discovered it?

A

cause sterile maleness if homozygous in XX (should be F), XY males unaffected

sturtevant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a bilateral gynandromorph

A

mosaic of 2 phenotypes across one axis of their body

studied by crossing F who were double het for X linked traits (mini wing and white eye) with M who were dom for those traits

offspring developed F side (dom traits) and M side (rec traits)

after 16 cell stage, one cell lost the X chrom with the dominant alleles –> cells that arose from that cell developed as M with recessive alleles; other cells had 2X and developed as het F

23
Q

What is ZW sex determination? What types of organisms use it?

A

like XY, but F is the heterogametic sex (F = ZW)

nonavian repriles, birds, butterflies

24
Q

Why are white throated sparrows unique? How many effective sexes do they have? What is the evolutionary significance?

A

4 sexes

Tan and white morphs –> tan M, tan F, white M, white F

same color never mate with each other

evolutionarily transient (not sustainable) bc it decreases the chance of finding a mate

25
Q

What is haldane’s rule and the evolutionary significance?

A

When 2 closely related species are crossed and one sex of the hybrid is sterile or missing, that is the heterogametic sex

first step in reproductive isolation –> speciation

26
Q

what is sequential hermaphroditism

A

when individuals of a species start life as one sex and transition to the other

27
Q

What’s the only known case of sequential hermaphroditism? How does it occur?

A

clownfish all start as M –> largest in the social group becomes F

turn M spec genes off and F spec genes on (make aromatase –> converts androgens to estrogens)

28
Q

What’s temperature GxE sex determination? What organisms does it occur in?

A

temperature determines aromatase activity but effect varies across species (temperature dependent sex determination and genotype by environment interaction)

many reptiles

29
Q

What is haplodiploidy? whata’s the effect on relation and deleterious alleles?

A

sex determination in hymenoptera

haploid (unfertilized egg) = male

diploid (fertilized egg) = female

sisters are more closely related than in diplodiploids (genes from dad - half of their genetic material is the same)

deleterious alleles immediately revealed in males bc they are haploid

30
Q

What is unique about platypus/monotreme sex determination?

A

use XY sex determination but have 10X (F) or 5X and 5Y (M)

exception to mendel independent assortment (male meiosis makes multivalent chain to separate all X from all Y –> each gamete has either X or Y, not a mix of both)

most basal mammals

31
Q

How is sex determined in humans? How do we know?

A

XY, presence of the Y = male, absence of Y = female

XXY = male

X = female

32
Q

Disorders of abnormal human sex chrom karyotypes?

A

XXY = klinefelter syncrome

X = turner syndrome

Y = inviable embryo

XXX = triplo X

XYY = jacobs syndrome

33
Q

phenotypes of human sex chrom disorders

A

Klinefelter: male, testes, little sperm, infertile except for IVF, some F secondary sex char, intellectual disability common

turner: female, ovaries, usually infertile, short stature, normal intelligence, can be mosaic with less severe phenotype

triplo X: female, can be entirely normal, can have underdeveloped secondary sex char, sterility, and intellectual delays

Jacobs syndrome: discovered by patricia jacobs, can be entirely normal, can be taller, have antisocial tendencies, intelligence deficits (lots in scottish prison)

34
Q

Why can humans tolerate aneuploidy in sex chrom better than autosomes

A

Y is not necessary for life/does not have a lot of genes –> extra dose not an issue

X inactivation in mammals turns all but 1 X into barr bodies (dosage comp)

35
Q

What is dosage compensation and its purpose?

A

compensating for aneuploidy/abnormal number of copies of genes/chromosomes

ensures M and F have same amt of gene expression even if they don’t have the same number of genes/chromosomes

36
Q

how do c. elegans do dosage compensation?

A

halve expression of each X in hermaphrodites –> equal to males with 1 X (via DCC - c. elegans dosage compensation complex)

37
Q

how do drosophila melanogaster do dosage compensation?

A

double expression of single X in males –> equal to females w/ 2X (via DCC - drosophila dosage compensation complex)

38
Q

how do humans do dosage compensation?

A

decrease X expression in F (condense all but 1 X to barr bodies to match male expression)

X chromosomes have 4 genes in X inactivation center –> make XIST RNA (x-inactive specific transcript) –> binds to X chrom, recruits other proteins –> condensation

39
Q

How can timing of X inactivation make mosaics? Examples?

A

sometime after 16 cell stage

different cells can inactivate different Xs (independent)

inactivated X inherited by daughter cells (epigenetic inheritance)

lyon hypothesis ^^^ (mary lyon/liane russell)

if cat has an X with a dark allele and other X has orange allele, and dif X inactivated in dif cells –> calico

40
Q

what’s the human equivalent of a male calico cat

A

klinefelter (XXY)

41
Q

Why is X inactivation a form of imprinting?

A

one copy expressed, one copy suppressed

42
Q

what is genomic imprinting?

A

in an individual, one copy of a gene is expressed and the other is suppressed

43
Q

Compare and contrast sex determination in C. elegans and Drosophila

A

Sim:
1) rule for sex determination
ratio X:autosomes determines sex (1:2 = male)/male hemizygous for X

dif:
1) Type of sex chromosomes
c. elegans use XO, male = XO, hermaphrodites = XX

drosophila use XY, male = XY (XO sterile), female = XX

2) Method of dosage compensation
c. elegans halve expression of X in hermaphrodites

drosophila double expression of X in males

44
Q

Compare and contrast sex determination in humans and Drosophila. What is the sex in both species of XXY and X individuals?

A

sim: Type of sex chrom
1) both use XY

dif:
1) rule for sex determination
drosophila: ratio X:autosomes (1:2 or less = male, 1:1 or more = female)

humans: presence of Y = male

2) method of dosage compensation
drosophila double X in males

humans inactivate all but one X in females

XXY human = male (klinefelter)
XXY drosophila = female

X human = female (turner)
X drosophila = sterile male

45
Q

For these human karyotypes, give the sex and a common phenotype associated with the karyotype: X,XXX,XYY,XXY, Y

A

X = F, turner, small stature, usually infertile, normal intelligence

XXX = F, triplo X, some normal/unnoticeable, some intellectual and motor delay

XYY = M, Jacobs, some normal, others taller/anti social/less intelligent/fertility problems

XXY = M, klinefelter, infertile except for IVF, female secondary sex char

Y = inviable

46
Q

How do the phenotypes of XXXX and XXXXX individuals compared to XXX individuals inform our understanding of dosage compensation in humans?

A

PPl w/ 4 or 5X have more severe triplo-X symptoms

Even though humans achieve dosage compensation by deactivating all but one X chromosome, they’re not entirely deactivated and still affect gene expression to a small extent

46
Q

Why are gonadal ridges considered bipotential glands

A

turn into testes or ovaries depending in sex chrom

47
Q

How do we know that the SRY gene specifies maleness? What type of gene is SRY?

A

if XX with SRY gene –> male gonads

if XY but no SRY gene –> ovaries

SRY is a transcription factor

48
Q

What regions of the Y chrom are and are not homologous with the X chrom

A

PAR pseudoautosomal region IS

male specific region IS NOT

49
Q

what’s the primary sex ratio

A

sex ratio of conceived zygotes

50
Q

what’s the secondary sex ratio

A

ratio of babies actually born

51
Q

are the primary and secondary sex ratios 1:1? what’s an explanation?

A

secondary IS NOT, primary PROBABLY IS

zygotes formed at 1:1 ratio from independent assorment and random gamete union but secondary ratio favors males bc greater F mortality

52
Q

3 assumptions for primary ratio being 1:1

A

1) law of segregation = 50% X sperm and 50% Y sperm

2) equal survival and motility of X/Y sperm in F repro tract

3) egg surface equally receptive to both X/Y sperm

Genetics (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions