Genetics Flashcards
State which strands in DNA replication are the leading and lagging strands
5’ —> 3’ leading strand
3’ —> 5’ lagging strand
What are some defects of DNA that can occur
DNA strand breaks
Chemical cross linking occurs
Missmatched bases
Give a general overview of the process of meiosis
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
What are the coding regions of a gene?
Exons are the coding regions, and introns are the non-important parts that become spliced out when mRNA is transcribed and modified
What are the factors that limit the rate of translation?
Rate of transcription
Rate of splicing of mRNA to mature mRNA
The half life of mRNA
Rate of processing of the polypeptide
Define a polymorphism
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
Define a mutation
A gene change that causes genetic disorders
Heritable change in the human genome
Describe the structure of a chromosome superiorly to inferiorly
Telomere Short arm (p) Centromere Long arm (q) Telomere
Describe how chromosome banding occurs
Dna is wound around histone proteins, and where it is most tightly wound it produces a dark region.
What can be used to identify chromosomes
The banding pattern
Length of the chromosome
Position of the centromere
What is an acrocentric chromosome?
A chromosome without a short arm but instead a stalk containing ribosomal genes
What is FISH and what does it test
A fluorescent dye that identifies specific sequences in DNA e.g HER2 in cancer
What is an aCGH and what does it test? Limitations?
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
What is a balanced Vs unbalanced abnormality
Balanced; all chromosomal material present just not in the right place
Unbalanced; extra or missing chromosomal material
What is an aneuploidy
Where there is an entire extra or missing chromosome
What is robertsonian translocation
Where two acrocentric chromosomes become stuck together by their stalks.
What is PCR?
- allows amplification for a small gene sequence.
What is Next generation sequencing
Sequences huge chunks of genes, can do the entire genome
What is sanger sequencing? What can it identify
Can sequence dna, and identify small insertions and deletions in genes
What is a missense mutation? Give an example of a missense mutation
Where a non-functioning protein or a different protein is produced
E.g base change, deletion, insertion
What is mendelian inheritance? Give examples of this
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.
Define penetrance
Number of individuals who have a gene mutation who express clinical symptoms of it
What are some non-mendelian inheritance issues?
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
What are some mechanisms for DNA repair?
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
What is achondroplasia
Dwarfism caused by the mutation of the FGFR3 gene
What chromosomes are involved with down syndrome? What is it?
It involves a trisomy of chromosome 21
Causes physical growth delays, intellectual disability, facial features characteristic of the disease.
What is Edwards syndrome? What chromosomes are involved?
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
What is Turners syndrome?
What chromosomes are involved?
Affects development in females, results in short stature, loss of ovarian function
Only has one X chromosome
What is Triple X syndrome?
What does it involve
Three x chromosomes
No unusual physical features, just taller than average.
What is klinefelter syndrome?
What does it involve?
Occurs in males, where they have two X chromosomes, so XXY
Produces small testicles and sterility
What is Digeorge syndrome?
What does it involve?
(George- kids)
Deletion of segment of chromosome 22
Causes congenital heart problems, specific facial features, underdeveloped parathyroid and thymus, low set ears.
What is the philadelphia chromosome?
Gene abnormality in chromosome 22. Particulary leukemic cancer cells
What is retinoblastoma ?
Dominant, recessive?
Cancer of the cells in the retina (eye)
Dominant
