Medical Genetics Wk 11

Question 1

Types of mutations

Answer 1

Genome mutation - chromosome missgregation e.g aneuploidy

Chromosome mutation- chromosome rearrangement e.g translocations

Gene mutation- base pair mutation e.g point mutations

Question 2

Chromosome anomalies

Answer 2

Numerical-
- aneuploidy - sex or autosomal chromsome
- trisomy (gain of 1 chromosome)
-tetrasomy (gain of 2 chromosome)

Polyploidy- triploidy, tetraploidy

Structural-
Translocation
Inversions
Deletions
Insertions
Rings
Isochromosomes

Question 3

Aneuploidy

Answer 3

Aneuploid is an individual organism whose chromosome number differs from the wild type by part of a chromosome set.

Question 4

Nondisjunction in mitosis

Answer 4

Nondisjunction in mitosis or meiosis is the cause of most aneuploids.

Question 5

Nondisjunction during the first and second meiotic divisions

Answer 5

In both cases, some of the gametes that are formed
either contain two members of a specific chromosome or lack that chromosome.

Question 6

Nondisjunction during + Nondisjunction during egg development sperm development

Answer 6

LOOK AT GOODNOTES

Question 7

Klinefelter syndrome

Answer 7

also known as the XXY condition, is a term used to describe males who have an extra X chromosome in most of their cells. Instead of having the usual XY chromosome pattern that most males have, these men have an XXY pattern.

●Symptoms:
●Taller than average stature.
●Longer legs, shorter torso and
broader hips compared with other boys. ●Absent, delayed
or incomplete puberty.
●After puberty, less muscle and
less facial and body hair compared with other teens.
●Enlarged breast
tissue (gynecomastia)

Question 8

Triple X syndrome

Answer 8

also known as trisomy X and 47,XXX, is
characterized by the presence of an extra X chromosome in each cell of a female. Those affected are often taller than average.
taller than average
Complications
Learning
difficulties, decreased muscle tone, seizures, kidney problems

Question 9

Turner syndrome - 45 Chromosomes (monsomy X)
45,X

Answer 9

The sperm was either missing an X or Y chromosome or the egg was missing the X chromosome and the sperm carried the Y chromosome

Female baby

Symptoms- wide neck and small Jaw, small stature, learning disabilities, autism, lack of puberty, early menopause, infertility

Affected people have a characteristic, easily recognizable phenotype: they are sterile females, are short in stature, and often have a web of skin extending between the neck and shoulders.

Question 10

Trisomy

Answer 10

21- Down syndrome
18- edwards syndrome
13- Patau syndrome

Trisomy (‘three bodies’) means the affected person has 47 chromosomes instead of 46.

Question 11

Edward syndrome

Answer 11

Malformed ears
Small mouth, jaw and short neck

Prominent sternum
Clenched hands with overlapping fingers
Flexed big toe and prominent heels
Back of the skull is prominent

Question 12

Edward syndrome

Answer 12

Trisomy-18 (2n=46,18+) (Edward Syndrome) is the second most common trisomy after Down Syndrome, and occurs in 1 / 4 ~ 8000 live births. It is three times as prevalent in newborn girls as in boys. Trisomy 18 is characterized by microcephaly, a high forehead, profound psycho-motor retardation, and serious heart malformations. Life expectancy is typically very short: 90% of children die in the first year.

Question 13

Patau syndrome - trisomy 13

Answer 13

Small head
Small or missing eyes
Heart defects
Extra fingers
Abnormal genitalia
Mentally retarded
Cleft palate
Most die a few weeks after birth

Question 14

Down syndrome

Answer 14

In the karyotype, three members of the G-group chromosome 21 are present, creating the 47,21+ condition.

Question 15

Down syndrome

Answer 15

Risk increases with maternal age

Question 16

Incidence of Down syndrome births related to maternal age

Answer 16

Most children with Down syndrome have: ●Distinctive facial features, such as a flat face, small ears, slanting eyes, and a small mouth. ●A short neck and short arms and legs.
●Low muscle tone and loose joints. Muscle tone usually improves by late childhood. ●Below-average intelligence.
●Many children with Down syndrome are also born with heart, intestine, ear, or breathing problems.
●These health conditions often lead to other problems, such as airway (respiratory) infections or hearing loss. But most of these problems can be treated.

Question 17

Polyploidy

Answer 17

Polyploidy, the condition in which a normally diploid cell or organism acquires one or more additional sets of chromosomes.

Triploid 3N
Tetraploid 4N

Question 18

Triploid syndrome 69 Chromosomes

Answer 18

Either the sperm if egg has two full sets of chromosomes leading to a Triploid baby. TBs either miscarry or die in their first week of life

Triploidy in humans and most other animals is incompatible with life.