Genetics Flashcards
Strands of dna are replicated how?
5–>3 direction and pair up int anti parallel directoin
4 bases:
thymine-adenine
guinine-cytosine
sugar phosphate back bone
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DNA strand associates with proteins (including Histones) and is wound into a structure called a chromosome
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DNA can be damaged during replication, repair mechanisms exist, when these are defected, disease occurs
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cell cycle:
G1–>S–>G2–>M–>G1
what occurs at the s phase
DNA synthesis
function of DNA helicase
unzips DNA
function of DNA polymerase
copies 5-3 strand and 3-5 strand in okazaki fragments
funtion of DNA ligase
joins okazaki fragments
mitosis
One diploid parent cell becomes 2 identical diploid daughter cells
meiosis
One diploid parent cell becomes 4 haploid daughter cells
Crossing over occurs
Gamete formation
RNA
single stranded
ribose sugar
uracil replaces thymine
Transcription/Translation
DNA transcribed to pre mRNA
Pre mRNA spliced (removal of introns [non-coding sections of DNA] to mRNA
mRNA translated to protein
3 bases encode 1 amino acid or a stop codon
Protein is modified and moved around the cell
variation between cells
changes in promoter sequence
changes in exon sequence
cell cycle more detail
GO cell cycle: most cells are resting, carrying out their normal function
G1 cell cycle: 1st growth phase as chromosomes become ready to be replicated
S phase: DNA replication
G2 cell cycle: 2nd growth phase involving proteins
M phase: mitosis, mechanical separation of cell into two daughter cells. Identical, diploid cells
23 pairs of chromosomes
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SNPs (Single Nucleotide Polymorphisms)
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where do mutations occur in the cell cycle
between G2 and M or between G1 and S
how does variation occur in meioisis
- Crossing over
- Independent segregation of homologous chromosomes
what is polymorphism
a change in the genome that does not cause disease in its own right but can predispose to a common disease