Sex determination and sex chormosomes

Question 1

the process by which an embryo develops into either a male or female, influenced by genetic, hormonal, and developmental factors

Answer 1

sexual differentiation

Question 2

chromosomes, such as the XY pair in mammals, characterize one sex or the other in a wide range of species, resulting in their label as sex chromosomes

Answer 2

heteromorphic, chromosomes

Question 3

Nevertheless, it is genes, rather than chromosomes, that ultimately serve as the underlying basis of

Answer 3

sex determination

Question 4

butterflies have a different sex determination system compared to humans. Instead of X and Y chromosomes, they use a ZW system where females have ___, while males ___

Answer 4

females have (ZW)
males have (ZZ)

Question 5

As a result, they are described as the _________ and in effect, their gametes ultimately determine the sex of the progeny in those species.

Answer 5

heterogametic sex

Question 6

In such cases, the female, which has like sex chromosomes, is the ___________, producing uniform gametes with regard to chromosome numbers and types.

Answer 6

homogametic sex

Question 7

The male is not always the heterogametic sex

Answer 7

true

Question 7

To immediately distinguish situations in which the female is the heteroga metic sex, some geneticists use the notation

Answer 7

ZZ/ZW
ZZ/ZO

Question 7

The regulation of sex determination in C. elegans involves a combination of

Answer 7

genetic and environmental factors.

Question 8

does not have conventional sex chromosomes.

Follows a system of chromosomal dosage compensation to determine its sexual fate.

Answer 8

C. elegans

Question 8

Why is rare to do hybridization in animals?

Answer 8

strong reproductive isolation barriers that prevent successful interbreeding

Question 8

When does the XOL-1 gene manifests in C. elegans?

Answer 8

However, when the X:A ratio is reduced, the expression of XOL-1 is upregulated, leading to male development.

Question 8

The key gene involved in The regulation of sex determination in C. elegans is called the ________

Answer 8

XOL-1 (XO lethal) gene

Question 9

In C. elegans
it acts as a transcription factor that inhibits the hermaphrodite developmental pathway and promotes male development.

Answer 9

XOL-1

Question 10

explain how the XOL-1 gene affects the sex of the C. elegans

Answer 10

it is innately present in C. elegans, but inhibited by the XX chormosome. This makes everyone with an XX chromosome a hermaphodite.

Whenthe X:A ratio is reduced against the odds, the XOL-1 gene is not inhibitted and creates a male

Therefore any hermaphrodite mating with the male has a 50% chance of creating male offspring as opposed to 1%

Question 11

XOL-1 gene is negatively regulated by the presence of ___________, ensuring that most individuals develop as hermaphrodites.

Answer 11

two X chromosomes (XX)

Question 11

refers to the number of X chromosomes compared to the number of sets of autosomes (non-sex chromosomes) in an organism

Answer 11

X:A ratio

Question 12

with respect to primary sex determination, male gametes containing one of each auto some plus a Y chromosome result in male offspring not because of the presence of the Y but because they fail to contribute an X chromosome. This mode of sex determi nation is explained by the

Answer 12

genic balance theory

Question 13

what organism is said to have the ratio of X chromosomes to haploid sets of autosomes (A) determines
sex.

Answer 13

Drosophila

Question 14

in Drosophila, Normal males have a ratio of

Answer 14

0.5

Question 15

in Drosophila, Normal females have a ratio of

Answer 15

1

Question 16

in Drosophila, intermediate ratios produce __________ flies that expressed both male and female morphology

Answer 16

sterile intersex

Question 17

in Drosophila, Metamales have a ratio of

Answer 17

< .5

Question 18

in Drosophila, intersex have a ratio of

Answer 18

.5>1

Question 18

was doing classical genetics on fruit flies, looking for mutants and checking out the patterns of inheritance He studied the white eye phenotype and discovered something odd

Answer 18

Thomas Hunt Morgan

Question 19

Ratios below and above the normal produce infertile and _______________, respectively.

Answer 19

weak metamales or metafemales

Question 20

type of inheritance where Carrier mother passes allele to son who expresses it, passes allele to daughter who carries it, etc.

Answer 20

criss cross inheritance

Question 20

is a phenomenon where the temperature at which eggs are incubated during a critical period of development determines the sex of the offspring.

Answer 20

Temperature-dependent Sex Determination (TSD)

Question 21

what were Thomas Hunt Morgan's findings in drosophila eye color

Answer 21

+ The traits of sex and eye color did not assort independently (as the traits in peas did). + The traits are linked. + The gene is NOT PRESENT on the Y chromosome.

Question 22

Turtles have what type of Temperature-dependent Sex Determination (TSD)

Answer 22

type 1a

Question 22

tuataras have what type of Temperature-dependent Sex Determination (TSD)

Answer 22

type 1b

Question 22

crocodiles have what type of Temperature-dependent Sex Determination (TSD)

Answer 22

type II

Question 23

TSD have no Sex Chromosomes Involved

Answer 23

true

Question 24

Incubation temperature directly influences gene expression that triggers male or female development

Answer 24

Temperature-dependent Sex Determination (TSD)

Question 25

Critical Temperature-Sensitive Period (TSP) typically occurs during the ____________

Answer 25

middle third of incubation

Question 25

3 types Temperature-dependent Sex Determination (TSD)

Answer 25

Type la Type Ib Type II

Question 26

the specific time during embryonic development when the sex of an organism with temperature-dependent sex determination (TSD) is irreversibly determined by temperature

Answer 26

Critical Temperature-Sensitive Period (TSP)

Question 26

Critical Temperature-Sensitive Period (TSP) Lower temperatures → males, higher temperatures → females (common in many turtles)

Answer 26

Type la

Question 27

Critical Temperature-Sensitive Period (TSP) Lower temperatures → females, higher temperatures → males (some lizards)

Answer 27

Type Ib:

Question 28

results from non-disjunction an abnormality in the number of chromosomes in a cell due to loss or duplication

Answer 28

Aneuploidy

Question 28

Genes for male pathways

Answer 28

SOX9

Question 29

Critical Temperature-Sensitive Period (TSP) Intermediate temperatures → males, both low and high extremes → females (e.g., some crocodiles and snapping turtles)

Answer 29

Type II

Question 29

what happeens when homologues fail to separate during Meiosis I?

Answer 29

all resulting cells have the wrong number of chormosomes

Question 29

an enzyme that converts androgens to estrogens, is often more active at female-producing temperatures.

Answer 29

Aromatase

Question 30

Genes for female pathways

Answer 30

FOXL2

Question 30

Sex determination studies began in late

Answer 30

1800's

Question 31

Keys to understanding sex determination in humans:

Answer 31

Improved karyotype methods Study of aneuploidy of sex chromosomes Aneuploidy is the wrong number of a particular chromosome.

Question 32

what happeens when sister chromosomes fail to separate during Meiosis II?

Answer 32

half of the 4 cells have the wrong number of chormosomes

Question 33

a genetic syndrome where they are male in appearance, but some feminization; sterile. slow to learn, but not retarded. show the amt of chromosomes and the disorder in the sex chromosomes

Answer 33

XXY Klinefelter 47

Question 34

similar to XXY Klinefelter

Answer 34

XXXY etc. similar, but more severe symptoms

Question 35

a genetic syndrome where there is Monosomy, the only one occurring in humans. female, sterile, short webbed neck, broad chest, short. majority aren't born

Answer 35

45, XO Turner syndrome

Question 36

If XXY is still male and XO is female Y must be determinant of maleness

Answer 36

If XXY is still male and XO is female Y must be determinant of maleness

Question 37

Y chromosome has been shrinking. Now missing many of genes that X has.

Answer 37

true

Question 38

Region in Y chromosome where it contains the: X-transposed region X-degenerative region Amplicon region

Answer 38

MSY Region

Question 39

MSY Regions: 99% identical to X chromosome region, but only 2 genes; the rest are not expressed.

Answer 39

X-transposed region

Question 39

Regions near p telomere and q telomere homologous to X chromosome Crossing over can occur there during meiosis. Because of this, genes in this location do not behave as sex-linked traits, thus said to be pseudoautosomal because they behave like genes on autosomes rather than sex chromosomes.

Answer 39

PAR

Question 39

MSY Region that codes for testis- determining factor, necessary for maleness during development.

Answer 39

SRY

Question 40

MSY Regions: Contains DNA related to X chromosome regions Several functional genes and pseudogenes Contains SRY

Answer 40

X-degenerative region

Question 40

MSY Regions: Highly similar or repeated genes, some related to male development and fertility.

Answer 40

Amplicon region

Question 40

regions on the X and Y chromosomes in mammals that behave like autosomal regions during inheritance

Answer 40

pseudoautosomal

Question 41

If Male with two X chromosomes; SRY found on _

Answer 41

one Y

Question 41

Contains gene for testis determining factor

Answer 41

SRY

Question 41

If Female with X and Y; _______ is missing from Y

Answer 41

SRY

Question 41

In Transgenic mice, Remove SRY from Y chromosome Mice are XY but are ________ Reciprocal experiment also done

Answer 41

female

Question 42

SRY:

Answer 42

Sex-determining region of the Y

Question 42

PAR:

Answer 42

Pseudoautosomal region

Question 43

MSY:

Answer 43

Male-specific region of the Y

Question 44

is the number of copies of a particular gene present in a genome. related to the amount of gene product (proteins or functional RNAs) the cell is able to express

Answer 44

Gene dosage

Question 44

It matters how many copies of genes there are.

Answer 44

true

Question 45

1 set of genes on the X is good for males, is two sets (2 X chromosomes) bad for females?

Answer 45

No, having two X chromosomes in females does not inherently mean it's bad. In fact, it offers advantages, particularly in the context of X-linked genes. While males have only one X chromosome, females have two. This leads to a mechanism called X-inactivation, where one of the X chromosomes is randomly and permanently inactivated in most cells

Question 45

example of why It matters how many copies of genes there are?

Answer 45

Snapdragons: heterozygous flowers are pink. Multiple histone genes. Too many of some genes is deleterious. trisomy 21 = 3 copies of the chromosome 21 Petunia purple gene = purple gene duplicated too much = became white

Question 46

Y chromosomes are missing most of the genes that X has.

Answer 46

true

Question 46

hypothesized that this was an inactivated X chromosome in females so that there would only be 1 functional copy of genes, as in males.

Answer 46

Ohno

Question 47

noticed that in the nucleus of females, but not males, a darkly staining body is visible.

Answer 47

Murray Barr

Question 47

Dosage compensation authors

Answer 47

Murray Barr, Susumu Ohno, and Mary Lyon

Question 48

Inactivated X is called a

Answer 48

Barr body

Question 48

In placental mammals, it can be either X chromosome. All the descendents of that cell have the same X chromosome inactivated. what does this result to?

Answer 48

Results in a mosaic, patches of tissue with different lineages.

Question 49

Individuals with incorrect numbers of sex chromosomes have appropriate number of

Answer 49

Barr bodies

Question 49

XXX females have how many Barr bodies

Answer 49

2

Question 50

hypothesis where X chromosome inactivation takes place early in development.

Answer 50

Lyon Hypothesis

Question 51

author of lyonization

Answer 51

Mary Lyon

Question 52

is the inactivation of X random?

Answer 52

the process where one of the two X chromosomes in female mammals is randomly inactivated in each cell during early development. This inactivation prevents females from having twice as many gene products from the X chromosome compared to males, who have only one X chromosome.

Question 53

example of lyonization

Answer 53

+ Classic example: the calico cat. + One X chromosome codes for orange fur, the other for black. Cat shows characteristic mosaic patterns caused by one or the other X chromosome being inactivated. + White fur results from the effect of another gene.