Exam 3: Inheritance Flashcards
1
Q
humans have approx. ____ genes located on _____ chromosomes
A
23,000
46
2
Q
chromosomes occur as _____ homologous pairs in ____ form
A
23
diploid
3
Q
22 pairs are referred to as
A
autosomal
4
Q
the 23rd pair is what pair??
A
sex-determining pair (XX, XY)
5
Q
meiosis results in gametes that are ____
A
haploid
- containing one chromosome from each pair
6
Q
what restores the diploid number
A
fertilization
7
Q
genotype vs phenotype
A
genotype: genetic makeup
phenotype: physical expression
8
Q
allele
A
variation of gene
9
Q
locus
A
location of a gene on a chromosome
10
Q
in simple inheritance, what is controlled by the interaction of one pair of alleles?
A
phenotype
11
Q
homozygous
A
alleles in a pair that can be identical in expression
12
Q
dominant
A
alleles that are expressed in phenotype
13
Q
recessive
A
alleles that are masked by another allele’s expression
14
Q
when can a recessive phenotype be expressed?
A
only in the homozygous state
15
Q
when you have 2 diff alleles what interactions exist? (3)
A
complete dominance
codominance
incomplete dominance
16
Q
complete dominance
A
one allele expressed as phenotype, the other is masked
17
Q
codominance
A
both alleles fully expressed in phenotype
18
Q
incomplete dominance
A
the phenotype is an intermediate expression of the 2 alleles
19
Q
free earlobes, freckles, astigmatism, myopia or hyperopia, Rh+ factor, A or B blood type, Huntington’s Disease
A
dominant traits complete dominance
20
Q
normal vision, short eyelashes, having 5 fingers, Rh-, O blood type, Tay-Sachs, Phenylketonuria
A
recessive traits complete dominance
21
Q
2 complete dominance disorders
A
Huntington’s disease and Tay Sachs
22
Q
Huntington’s Disease
A
neurodegenerative disorder, symptoms occur midlife
- motor impairments
- wild jerky movements (chorea)
- insoluble aggregates
23
Q
Tay Sachs
A
autosomal recessive
- loss of group of enzymes that help break down lipids in CNS
- lysosome storage problem
- lazy baby syndrome
24
Q
Application: Complete Dominance Disorder
A
Familial Hypercholesterolemia
25
Familial hypercholesterolemia
dominant disorder that impairs LDL removal
| - high cholesterol levels due to genetics - dieting will not change this
26
HDL
good cholesterol
27
LDL
bad cholesterol
| - gets distributed to cell, if high it is bad - excess deposits in blood vessels causing plaque formation
28
what 3 genes involved in familial hypercholesterolemia
- mutation in gene encoding for LDL receptor
- mutations in ApoB encoding gene impair ability of LDL to bind to receptor
- mutations in regulating protein can diminish recycling of receptor causing abnormally low levels
(cannot put receptors back on membrane)
29
Discuss how even a healthy diet these mutations in familial hypercholesterolemia would still result in high serum cholesterol levels?
- mutations prevent LDLs from going into cell - stays in bloodstream, delay in receptors getting out to surface
30
Risks with high cholesterol levels
- plaque build up in blood vessels - affects blood flow to heart, brain - heart attack, stroke
31
Would you expect the risks to be different in an individual who is homozygous vs heterozygous for one of the familial hypercholesterolemia mutatios?
no
| - bc complete dominance only need one gene for this
32
Example of codominance
AB blood type
| - both alleles for gene equally expressed
33
Example of Incomplete dominance
Thallassemia
34
Thallassemia
```
can occur in alpha or beta globin gene
- major form = homozygous
- minor form = heterozygous
can cause anemia
lower O2 carrying capacity - fatigue
- incomplete bc carrier has symptoms
```
35
Penetrance
not all people who have a specific genotype express the phenotype
- neurofibromatosis
36
neurofibromatosis
- autosomal dominant
- if simple inheritance expect to see people with swellings
- only see symptoms in 50-80%
- if not 100% then it is penetrance
37
expressivity
the degree to which the phenotype is expressed
- severity , could be 100% penetrance
- Marfan's syndrome
38
Marfan's syndrome
connective tissue disorder
- effects elastin fiber making ligaments less flexible
- people have longer limbs, taller, lower % subcutaneous fat, connects retina to back of eye, heart problems
- can just be tall and thin but others may have life threatening conditions
39
X - linked Sex linked traits
red - green color vision
clotting factor VIII
hypohidrotic ectodermal dysplasia (sweat glands)
Duchenne's muscular dystrophy
40
Y-linked Sex linked traits
TDF
SRY
Spermatogenesis genes
41
Men vs women with X linked traits
women would follow simple inheritance (may have one of these and one normal allele)
men (only get one X, so whatever is on it will show )- higher percent in men
- if give to son they would have it but if give to daughter it would depend on husband
42
Sex Influenced Traits: Baldness
baldness controlled by an autosomal gene on chromosome 20
- it is dominant in men but recessive in women
difference due to effect of androgens
expressed differently depending on if male or female
need one gene for baldness (women need to be homozygous)
43
Application: Pleiotropy - examples
one gene results in more than one phenotype
- Marfan's
- albinism
- sickle cell anemia
44
example of polygenic inheritance
eye color
45
EYCL 1 (gey) gene
locus on 19; green/blue
46
EYCL 2 (gey) gene
locus on 15; central brown/blue
47
EYCL 3 (gey) gene
locus on 15; brown/blue
48
How do you get blue eyes?
have to be recessive for all colors
49
How do you get brown eyes?
dominant for 2 and 3
50
What staining do karyotypes involve?
Giemsa staining forming G bands
51
which karyotype regions stain darker vs lighter?
A-T darker
| C-G lighter
52
euploid
refers to any exact multiple of a chromosome set (n)
| - monoploid or diploid
53
aneuploid
wen euploid does not apply -extra or missing chromosome
54
trisomy vs monosomy
trisomy - has extra chromosome
| monosomy - missing a chromosome
55
nondisjunction in meiosis II
centromere did not separate, did not chromosome for pair and one cell got both from the pair
- the one with chromosomes would be the trisomy (extra) the one with nothing would be monosomy (missing)
- only half abnormal in meiosis II
56
Nondisjunction in meiosis I
both would be in one cell, you would get 2 gametes missing chromosomes and 2 gametes with 2 chromosomes each
- higher percentage of having fertilized embryo with problems
- all abnormal
57
2 types of structural abnormalities and what are they?
deletions: portion of chromosome lost due to breakage or unbalanced crossing-over (translocation)
additions: due to translocation
58
translocation
unequal sharing - one loses info while the other gets too much
59
Genetics of Down's syndrome
```
most common - trisomy 21
47, XY +21
less common - translocation
46, XY t(21:21) or 46, XY t(14:21)
- can have all or part of 21 on 14
```
60
Clinical effects of Down's Syndrome
- growth retardation
- learning disabilities
- craniofacial abnormalities (eyes)
- cardiac defects: heart formation problems)
- poor muscle tone
- high risk of Alzheimer's
61
Genetics of Turner's Syndrome
only monosomy condition known to be survivable
45, X
presence of one X = female
ONLY in females!!!
62
Clinical aspects of Turner's Syndrome
- short stature on average
- lymphedema of extremities
- low placed ears
- webbed neck
- infertile - only have one X will not get through checkpoint in metaphase
63
Genetics of Cri du chat Syndrome
```
unbalanced translocation
loss of short arm in chromosome 5
partial monosomy
46 XY (5p-)
- means minus the short arm (p)
```
64
short arm vs long arm in cri du chat
short arm = p
| long arm = q
65
Clinical aspects of Cri du chat Syndrome
high pitched catlike cry in infants
microcephaly
intellectual disabilities
congenital heart disease
66
Genomic imprinting
- expression dependent on parent or origin
| - some genes always shut down in egg or always shut down in the sperm
67
2 types of Genomic imprinting
Angelman syndrome and Prader-Willi Syndrome
68
Angelman Syndrome
```
maternal origin
deletion from mother
- learning disabilities
- speech disorders
- poor motor development
- prone to seizures
- happy, frequent laughter
46, XX (15q11-15q13)
```
69
Prader-Willi Syndrome
```
paternal origin
- deletion from father
learning disabilities
poor muscle tone
compulsive eating
obesity
hypogonadism
hormone issues
```
70
Barr bodies
only one X chromosome needed to survive
- in development of females one X is inactivated in somatic cells. Both X remain active in germ cell line
- inactivation mainly random
- all cells descendant from the initial inactivated X cell will express same X chromosome
71
Effects of Barr Bodies (2)
mosaics
| fragile X syndrome
72
mosaics
- occurs in women who are heterozygous for X-linked traits
- result of random inactivation
- example: sweat gland distribution in patches of skin
calico cats
shut down early = big patches
shuts down late = tiny patches - tortoise shells
73
fragile X syndrome
- inherited from mother
- increased DNA repeats in inactivated X chromosome
- 46, XY (Xq-27) it will break
- learning disabilities
- large ears, jaw, testes
- some women carriers show cognitive effects
second most common form of learning disabilities
74
application: fragile X syndrome
- occurs due to a break in chromosomes, causing a low folate
- over 200 shuts down the gene and results in developmental issues
- sperm cannot carry mutated X but can pass on premutations
75
application: chromosomal abnormalities
turner's and klinefelter's
76
In klinefelter's would the disorder occur in men, women, or both?`
men
77
How could the condition of klinefelter's occur?
nondisjunction
| - in meiosis I or II
78
application: pseudoautosomal genes
PAR
on ends of sex chromosomes
when make barr body they are regions that do not shut down - so these regions are active even in barr bodies
- survives with one X but problems with deficiency
