Genetics

Question 1

State which strands in DNA replication are the leading and lagging strands

Answer 1

5’ —> 3’ leading strand

3’ —> 5’ lagging strand

Question 2

What are some defects of DNA that can occur

Answer 2

DNA strand breaks
Chemical cross linking occurs
Missmatched bases

Question 3

Give a general overview of the process of meiosis

Answer 3

Phase I; chromosomes duplicated, homologous chromosomes then line up (independent assortment) then cross over (exchange dna). The cell then splits into two cells.

Phase II; division of each of the two cells to produce 4 gamete cells that are haploid and genetic variants

Question 4

What are the coding regions of a gene?

Answer 4

Exons are the coding regions, and introns are the non-important parts that become spliced out when mRNA is transcribed and modified

Question 5

What are the factors that limit the rate of translation?

Answer 5

Rate of transcription
Rate of splicing of mRNA to mature mRNA
The half life of mRNA
Rate of processing of the polypeptide

Question 6

Define a polymorphism

Answer 6

A variation that doesnt directly cause a disease but may contribute to the disease.

Any variation with a frequency of 1% or greater in a population

Question 7

Define a mutation

Answer 7

A gene change that causes genetic disorders

Heritable change in the human genome

Question 8

Describe the structure of a chromosome superiorly to inferiorly

Answer 8

Telomere 
Short arm (p)
Centromere
Long arm (q)
Telomere

Question 9

Describe how chromosome banding occurs

Answer 9

Dna is wound around histone proteins, and where it is most tightly wound it produces a dark region.

Question 10

What can be used to identify chromosomes

Answer 10

The banding pattern
Length of the chromosome
Position of the centromere

Question 11

What is an acrocentric chromosome?

Answer 11

A chromosome without a short arm but instead a stalk containing ribosomal genes

Question 12

What is FISH and what does it test

Answer 12

A fluorescent dye that identifies specific sequences in DNA e.g HER2 in cancer

Question 13

What is an aCGH and what does it test? Limitations?

Answer 13

Microarray technique to test if there is an unbalanced arrangement of chromosomes (missing or extra chromosomal material).

Cannot test for balanced rearragments and mostly picks up neutral polymorphisms

Question 14

What is a balanced Vs unbalanced abnormality

Answer 14

Balanced; all chromosomal material present just not in the right place

Unbalanced; extra or missing chromosomal material

Question 15

What is an aneuploidy

Answer 15

Where there is an entire extra or missing chromosome

Question 16

What is robertsonian translocation

Answer 16

Where two acrocentric chromosomes become stuck together by their stalks.

Question 17

What is PCR?

Answer 17

• allows amplification for a small gene sequence.

Question 18

What is Next generation sequencing

Answer 18

Sequences huge chunks of genes, can do the entire genome

Question 19

What is sanger sequencing? What can it identify

Answer 19

Can sequence dna, and identify small insertions and deletions in genes

Question 20

What is a missense mutation? Give an example of a missense mutation

Answer 20

Where a non-functioning protein or a different protein is produced
E.g base change, deletion, insertion

Question 21

What is mendelian inheritance? Give examples of this

Answer 21

The manner that genes and traits pass from parents to their children based on a single gene mutation

Autosomal dominant, autosomal recessive, x-linked dominant, x- linked recessive.

Question 22

Define penetrance

Answer 22

Number of individuals who have a gene mutation who express clinical symptoms of it

Question 23

What are some non-mendelian inheritance issues?

Answer 23

Co-dominance; both alleles equally expressed
Multifactorial; genetic change adding a risk factor for getting a disease
Mitochondrial; contains genes for metabolic pathways if mutated then some daughter cells will have issues

Question 24

What are some mechanisms for DNA repair?

Answer 24

Base excision repair (BER)- repairs single damaged bases

Nucelotide excision repair (NER)- repairs damaged DNA like helix-distorting damage caused by UV light

Mismatch repair- corrects error not corrected by proof reading. Does this by endonucleases

Question 25

What is achondroplasia

Answer 25

Dwarfism caused by the mutation of the FGFR3 gene

Question 26

What chromosomes are involved with down syndrome? What is it?

Answer 26

It involves a trisomy of chromosome 21

Causes physical growth delays, intellectual disability, facial features characteristic of the disease.

Question 27

What is Edwards syndrome? What chromosomes are involved?

Answer 27

Involves a Trisomy of chromosome 18

Babies have small head, jaw and mouth, long fingers that overlap and in a clenched fist, low set ears, cleft lip and palate

Question 28

What is Turners syndrome?

What chromosomes are involved?

Answer 28

Affects development in females, results in short stature, loss of ovarian function

Only has one X chromosome

Question 29

What is Triple X syndrome?

What does it involve

Answer 29

Three x chromosomes

No unusual physical features, just taller than average.

Question 30

What is klinefelter syndrome?

What does it involve?

Answer 30

Occurs in males, where they have two X chromosomes, so XXY

Produces small testicles and sterility

Question 31

What is Digeorge syndrome?
What does it involve?

(George- kids)

Answer 31

Deletion of segment of chromosome 22

Causes congenital heart problems, specific facial features, underdeveloped parathyroid and thymus, low set ears.

Question 32

What is the philadelphia chromosome?

Answer 32

Gene abnormality in chromosome 22. Particulary leukemic cancer cells

Question 33

What is retinoblastoma ?

Dominant, recessive?

Answer 33

Cancer of the cells in the retina (eye)

Dominant