sex-linked traits

Question 1

who was the first person to associate a specific gene with a specific chromosome in the early 20th century

Answer 1

thomas hunt morgan

Question 2

what did morgan discover (fruit fliy experiemnt)

Answer 2

foundthat eye color gene was inherited in diff patterns by males and female flies
-eye colour gene was linked to sex, specifically found on x xhrom

Question 3

linked vs unlinked genes

Answer 3

linked=genes that are close together on same chrom
unlinked=genes not near eachother or on seperate chroms, not ususally inherited tg.for genes tht are far apart on same chrom chances of crossing over (prophase1) between homologous chroms

Question 4

(unlinked or linked?) genes follow mendels law of independent assortment

Answer 4

unlinked. linked genes do not follow mendels law of independent assortment bc they are close together and on the same chromosome so linked genes always inherited together (still have a chance of crossing over but v low)

Question 5

heterozygous for both genes crosses with homo for both genes, what should be the ratio if the genes were unlinked (crossing over occurs), completely linked (no crossing over at all)

Answer 5

1:1:1:1 (recombinants exist)
1:1:0:0 (no recombinnats)

Question 6

incomplete linkage

Answer 6

when recombinant pheno shows but not in an equal portion, way less than parental phenotypes in offspirng
–menas that genes are located very close on the same chrom but the short distance allows for a slight chance of crossing over to occur

Question 7

duchenne muscular dystrophy

Answer 7

-sex linked disorder due to the absence of an X-linked gene for a muscle a protien called dystrphin
-causes weakening in muscles
-1 in 3500 males in usa affected

Question 8

hemophilia

Answer 8

-sex-linked disorder
-absence of one or more clotting factors (13 proteins)
-individuals have prolonged bleeding
-can betreated w iv for missing proteins

Question 9

hypertrichosis

Answer 9

-sex-linked diseases
-excessive hair on face or body

Question 10

non-disjunction

Answer 10

-pairs o hom chroms do not seperate normally (at meiosis 1 or 2)
-gametes can contain either 2 or no chroms
large scale chromosomal alterations can lead to spontaneous abortioin or developmental disorders=anueploidy

Question 11

anueploidy

Answer 11

action in disjunction = occurrence of extra
or missing chromosomes due to
non-disjunction, which leads to an
unbalanced chromosome
complement (if organism survives,
aneuploidy typically leads to a
distinct phenotype
eg) down syndrome extra 21st chrom

Question 12

klinefelters syndrome

Answer 12

-XXY
-trisomy
-non-disjunction of sex chroms
male sex organs, female characteristics, sterile, normal intelligence

Question 13

monosomy X or Turner’s syndrome

Answer 13

-(X0 or X-)
-females are short, sterile and normal intelligence
“TURNER HAS MONO=turners is monosomy X)

Question 14

trisomy X

Answer 14

(XXX)
-healthy females with mild to severe symptoms of developmental delays (learning disabilites, delayed speech, language development)
-capable of reproducing but limited

Question 15

jacob’s syndrome

Answer 15

(XYY)
-trisomy
-taller than avg, below normal intelligence, nonsterile

Question 16

cri du chat

Answer 16

specific deltion in chromosme 5
-not aneuploid cond.
-results in distinct facial features, severe cognitive delyas, high pitched cry

Question 17

homomorphic vs heteromorphic chroms

Answer 17

homo=Morphologically identical chromosomes that make up a homologous pair (involving autosomes, XX genotype, ZZ genotype. same size shape and identical genes. but there may be little variation lik eone gene being mutated

hetero=Morphologically dissimilar (non-identical) chromosomes (involving XY
genotype and ZW genotype), diff size shape and genetic comp

Question 18

psuedoautosomal regions

Answer 18

(par1 and par2) behave like autosomes on the sex chroms (one either ends) nd can recombine during meiosis; crossing over

Question 19

male-specific region of the Y

Answer 19

MSY
-non-recombining region of Y chrom
95% of y chroms. divided equally between euchromatic regions (containing functional genes) and heterochromatic regions (lacking genes

Question 20

sry

Answer 20

-sex-determining region Y
located adjacent to PAR1 of the shprt arm of Y chrom
-Controls male development by encoding a protein called Testis-determining factor (TDF) – this is a transcriptional factor protein that elicits a cascade of gene transcription and developmental events that ultimately produce male internal and external structures
-At 6–8 weeks of development, SRY gene becomes active in XY embryos

Question 21

MIF

Answer 21

-The testis produces a hormone called MIF (Mullerian Inhibiting Factor), which causes degeneration of female organs

Question 22

t or f :Although female mammals inherit two X chromosomes, only one X chromosome is active

Answer 22

t

Question 23

Barr body

Answer 23

-During female development, one X chromosome per cell condenses
into a compact object called a Barr body
– Total number Barr bodies follows N − 1 rule (N = total number of X chromosomes)
o So, XX females have one Barr body per cell, XXX females have 2 Barr bodies per cell, and XXY Klinefelter males have one Barr body per cell (Barr bodies are not observed in XY males
-Most of the genes on the Barr-body chromosome are not expressed bc of compaction
-but will reexpress in ovarian cells that produce ova
-also stuck to nucleaur lining or wtv

Question 24

trace out the normal pathway for sex development (sry, tdf, mif etc.)

Question 25

what determines whih X chrom gets inactivated (barr body)

Answer 25

-occurs randomly and independently in embryonic cells at the time of X inactivation. either paternal or maternal x is deactivated

Question 26

can the silencing of one X chrom (barr body) have an affect on phenotypes??

Answer 26

-In most cases, the silencing of one X chromosome in each cell has no detectable effect on the function of a tissue or on the phenotype
– Occasionally, however, female carriers of X-linked recessive traits display a phenotypic manifestation of the recessive allele
eg) female cats can be orang and black patches of fur corresponding to portion of skin where each X chromosome is active.

Question 27

XIST

Answer 27

-special gene that helps “turn off” one of the two X chrom
-acts like a switch. It makes a special kind of molecule (RNA) that covers one of the X chromosomes and tells it to stop working. This process is called X-inactivation

Question 28

since one x xhrom gets deactivated how come the recessive allele doesnt show more often?

Answer 28

In many cases, it appears that having
50% of cells with the unaffected copy
of a gene is sufficient to produce the
unaffected phenotype

Question 29

whats the purpose of barr bodies

Answer 29

Purpose of Barr bodies is for dosage
compensation. This compensation is
the cell’s way of ensuring that the
volume of genetic material is balanced
between the sexes. Females, with
their two X chromosomes, could
theoretically have twice the amount
of X-linked gene products as males,
who have only one X.

Question 30

can a barr body be reactivated?

Answer 30

yes when cells within ovaries become eggs

Question 31

mode of inheritence of: pearson syndrome

Answer 31

mitochondrial (meaning on f can pass the allele but all kids will have it)
-causes probs w development of blood-forming cells in the bone marrow

Question 32

porcupine disorder

Answer 32

y-linked
-porcupine man-skin becomes tough and scaly

Question 33

rett syndrome

Answer 33

x-linked dominant
neuro disorder often in girls cuz its x dom

Question 34

hemophilia

Answer 34

x-linked recessive

Question 35

polydactyl

Answer 35

autosomal dominant
long fingers

Question 36

cystic fibrosis

Answer 36

autosomal recessive