Genetic stuff

Question 1

What are haploid cells?

Answer 1

cells that have 1 copy of each chromosome, typical state for games. In humans the haploid number is 23

Question 2

What is polyploidy?

Answer 2

• Presence of a complete set of extra chromosomes (ex: normal = 46 chromosomes, if you have polyploidy you will have 69 chromosomes)
• Occurs with meiotic failure (diploid sperm or egg cell) or dispermy (fertilization with 2 sperm)

Question 3

What is an autosomal aneuploidy?

Answer 3

• Cells that contain missing or individual chromosomes (not a multiple of 23 chromosomes)
• Primarily from nondisjunction
  
  • monosomy (1 copy of a chromosome in another wise diploid cell)
  • Trisomy (three copies of a chromosome)

Question 4

What is meitic nondisjunction?

Answer 4

It is a major cause of aneuploidy, an abnormal chromosome pattern in which the total number of chromosomes is not a multiple of the haploid number 23.

Question 5

What is Mosaicism?

Answer 5

• Presence of two or more chromosomally distinct cell lines in the same individual
• Extent (expressed as percentage) depends on the stage of embryonic development during which the cell division error occurs

Question 6

What are some characteristics of Mosaic Down syndrome?

Answer 6

• Female with mosaic Down syndrome is 46,XX/47,XX,+21.
• Results from mitotic nondisjunction during early embryonic development of a normal zygote. Affected children have mixed cell populations, some with the normal karyotype, others with the extra chromosome.
• The proportion of trisomic cells affects the child’s developmental potential and syndrome-associated potential health problems.

Question 7

What are some characteristics of turner syndrome?

Answer 7

• Only one X chromosome (usually females have two X chromosomes = XX)
• A monosomy that is compatible with life
• Verbal IQ > performance IQ
• Girls are infertile

Question 8

What are some physical characteristics of turner syndrome?

Answer 8

• Triangle-shaped face, posteriorly rotated ears, broad “webbed neck”, broad shield-like shaped chest, short stature
• May have lymphedema of hands and feet (observable at birth)
• Many have congenital heart defects and/or kidney defects
• Ovarian dysgenesis – do not develop secondary sexual characteristics, most are infertile

Question 9

Describe autosomal dominant inheritance

Answer 9

Question 10

Describe autosomal recessive inheritance

Answer 10

Question 11

What is a Genotype?

Answer 11

individual’s genetic material at a specific location

Question 12

What is a phenotype?

Answer 12

what is observable physically or clinically

Question 13

What is a homozygote?

Answer 13

an individual in whom the two alleles at a locus are the same

Question 14

What is a heterozygote?

Answer 14

an individual who has two different alleles at a locus

Question 15

Describe x-linked recessive inheritance

Answer 15

• Affected individuals are principally males.
• All carrier females are normal.
• All affected males have symptoms of the disorder.
• Males are not carriers.

Question 16

What are some characteristics of PKU and how would you treat it?

Answer 16

characteristics:

• 1 in 10,000 to 15,000 white births
• > 95% untreated PKU patients become moderately to severely cognitively impaired

Tx:

• Dietary restriction, low phenyalanine (before 4 weeks of age), effective in altering disease
• Avoid high protein foods (milk, cheese, eggs, nuts, soybeans, beans, chicken, beef, pork, fish, peas, beer, aspartame), yeast and gluten containing breads
• Limit certain fruits and vegetables (peas, corn on the cob, rice, crackers and snack foods, cookies