Genetics Flashcards
What is a karyotype and what is ideogram?
A karyotype is the complete set of chromosomes in a species. Human: 46, XX or 46XY
Ideogram - diagrams geneticist use as a standard representation from chromosome, showing the chromosomes’ relative size and banding patterns.
What are the parts of a chromosome? (long arm, short arm…)
The chromosome is made up of a centromere and two sister chromatids.
q = long arm, and p = short arm
How many pair of autosomes, and how many sex chromosomes do humans have?
22 pairs of autosomes
1 pair of sex chromosomes (x and y)
How does the medical and general usage of the word “gene” differ?
Medical terms: refers to only sequences that code for proteins
Outside medical terms: any functional unit of chromosome is referred to as a gene
What is a locus
The physical location of a gene on a chromosome. They are marked by “p” or “q” followed by a number
What are alleles
Two or more variation of a gene in a population
What is the difference between genotype and phenotype?
Genotypes - the specific combination of alleles that a person has for some locus
Phenotype - the results of the genotype, and observable trait. Ex: eye color
What is a SNP?
Single Nucleotide Polymorphism: a DNA sequence variation occurring when a single nucleotide (ATC or G) differs between members of a species or pared chromosomes in an individual.
What is the difference between imprinting of the X chromosome and imprinting of the autosomes?
X Chromosome INACTIVATION: the entire X chromosome is closed down and it can’t be accessed or used! Called a Barr body.
Imprinting of autosomes: When imprinting autosomes, you normally will just shut down one or a few genes on the chromosomes. You won’t shut down the entire chromosome.
What are the 5 points of control for gene expression? Which is most studies in terms of epigenetic influences?
- Chromatin Stage ***Most Studied! (winding and unwinding of chromatin to encourage or discourage gene expression
- Transcriptional Stage
- Translational Stage
- Post translational control of cytoplasm
- Post translational modification
Why does DNA naturally wrap around histones?
DNA is negative because of the phosphate groups and the histones are positive so they naturally attracted to each other.
What epigenetic changes can occur to histone tails to encourage or discourage winding/unwinding?
Histone methylation:
Addition of methyl group
Target sites are CpG Islands
Methylation of CpG Islands = DOWNREGULATION of transcription
Histone Acetylation:
Addition of an acetyl group
DNA is stopped from getting further condensed
Transcription is UPREGULATED
What is the promotor region on a gene, and why are promotor regions generally not methylated?
Promotors are at the start of genes where transcription factors bind. CpG islands are located near the promotor region. CpG islands are usually protected from methylation because that would silence/stop gene expression.
