Genetics

Question 1

What are the different types of DNA mutations?

Answer 1

• Single nucleotide polymorphism (base pair substitution)
  
  • only one amino acid in the entire protein is changed
  • common SNPs are what allows people to be different
  • If a single mutation happens to make a stop codon, this can cut the protein short and may be devastating
• Frame shift mutation with one base pair inserted or deleted
  
  • the entire rest of strand will be messed up
  • this is uncommon because the result would be devastating

Question 2

What are the single gene genetic disorders?

Answer 2

• Dominant- when having only one bad gene causes problems
• Recessive- when you need two defective genes to have a problem
• X-linked-
  
  • recessive: All the Xs need to be defective; this is a bigger problem for males because they only have one X (ex. duchenne’s)
  • Dominant: rare, few known- usually only seen in femalse b/c it would be fatal in males
• Y-linked- these usually result in infertility and are quickly bred out of the gene pool

Question 3

What are translocations and deletions?

Answer 3

• Translocation- genetic material from one chromosome is mistakenly put on another chromosome
• Deletion- genetic material deleted from a chromosome

Question 4

What is Aneuploidy?

Answer 4

• Nondisjunction (usually trisomy)
• Normal is to have 44 chromosomes + XX or XY
• can accidentally have three of any chromosome, but usually it is the higher numbered chromosomes because they dont carry as much information as the bigger ones and are more survivable
  
  • Trisomy 21- downsyndrome
  • Trisomy 18- Edward syndrome
  • Trisomy 13- Patau

Question 5

What is Turner syndrome?

Answer 5

• Type of Aneuploidy
• Female with only one X
  
  • only monosomy that survives to term
  • these females will be infertile
  • can become pregnant via IVF and HRT
• Normal intelligence, some mild cognitive problems
• Heart problems, often die around 50
• webbed necks, look pretty normal at first glance

Question 6

What is Klinefelter?

Answer 6

• A type of Aneuploidy
• Male has an extra X (47:XXY)
  
  • infertility is most common problem, but not all are infertile
• extra DNA is more tolerable than missing DNA
• Gynecomastia
• very mild cognitive impairement

Question 7

What is polyploidy?

Explain the watermelon thing

Answer 7

• Chromosome sets that don’t equal to 2
• Ex: Partial mole
  
  • two sperm into one egg
  • usually 69:XXY or 69:XXX
  • occasionally go to term but dont survive long
• Seedless Watermelon is bred to be infertile by taking a watermellon with 4 sets of chromosomes and mating it with a watermellon with 2 chromosomes
  
  • spawn is tetraploid and infertile so it has no seeds

Question 8

Definition:

locus

Answer 8

location in the genome

Question 9

Definition:

Allele

Answer 9

one member of a pair of genes

Question 10

Definition:

Genotype

Answer 10

the genetic material

Question 11

Definition:

Phenotype

Answer 11

the physical manifestation

Question 12

Definition:

penetrance

Answer 12

the chance that phenotype follows genotype

Question 13

Definition:

Haplotype

Answer 13

alleles on a single chromosome

Question 14

Definition:

Recombinations/crossover

Answer 14

gene rearrangement between homologous chromosomes

Question 15

What are the different parts of the chromosome?

Describe the different stages of Meiosis.

Answer 15

• Parts
  
  • P: the petit (short) arm
  • Q: the long arm
• Meiosis
  
  • Interphase S- duplication of each chromosome
    
    • have 4 copies of each somatic chromosome
  • Meiosis I (crossover)- some material from each chromosom switches over (this is how you get attributes from each parent) and then they separate homologous pairs into two separate cells
  • Meiosis II- each chromosome separates and they divide again so they each have one of each chromosome (ready to mingle with somebody else’s gametes)
  • Males make 4 sperm, females make 1 egg and 3 polar bodies

Question 16

What is nondisjunction?

Answer 16

• Where a set of chromosomes doesnt split appropriately in meiosis I or meiosis II
  
  • leads to trisomy or monosomy
  • Maternal age contributes to chance of trisomy

Question 17

What are some errors that can occur with crossover?

Answer 17

• uneven crossover- two copies are made, but one gamete would have two and the other wouldn’t get one
• Deletion- segment of chromosome is lost
  
  • we can tolerate additional DNA better than lost DNA

Question 18

What causes chromosome translocation?

Answer 18

• Cross-over between non-homologous chromosomes
• Ex: Chromosome 1 from mom and chromosome 2 from dad mix together
  
  • not supposed to happen, should only mix 1 and 1 or 2 and 2
• Would be ok if it is “balanced”, but chances are slight
  
  • Problems would arise when you try to make babies; you might end up with a bunch of miscarriages

Question 19

What are the autosomal dominant diseases mentioned?

Answer 19

• Familial hypercholesterolemia
• Huntington disease
• Achondroplasia
• Marfan
• Retinoblastoma
• Li-Fraumeni

Question 20

What are the autosomal recessive diseases mentioned?

Answer 20

• Sickle cell anemia
• Cystic fibrosis
• Lysosomal storage diseases
• Phenylketouria
• Glycogen storage diseases

Question 21

What are the X-linked problems mentioned?

Answer 21

• Duchenne muscular dystrophy
• Hemophilia A (factor VIII) and B (factor IX)