genetics Flashcards
what are the types of DNA in cells ?
bounded linear DNA in nucleus (eukaryotic)
unbounded circular DNA in mitochondria/chloroplast (eukaryotic)
unbounded circular DNA in cytosol (prokaryotic)
DNA structure
anti-parallel double helix
two complementary strands of nucleotides
5’ end & 3’ end nomenclature
nucleotide
nitrogenous base
deoxyribose sugar
phosphate group
bonds between DNA strands
weak hydrogen bonds between complementary base pairs
A & T : two hydrogen bonds
C & G : three hydrogen bonds
helicase
unwinds DNA
breaks weak hydrogen bonds between DNA strands
exposes nucleotide bases
polymerase
copies DNA
bonds complementary nucleotides from 5’ to 3’
proofreads new DNA strands
homologous chromosomes
pair of maternal & paternal chromosomes which carry the same genes, but may vary in alleles
independent assortment
homologous chromosomes line up & separate independently during metaphase I
results in random maternal & paternal chromosomal combinations
crossing over
recombination
recombination of genes between non-sister chromatids of homologous chromosomes during prophase I
results in recombinant chromatids creating unique genetic combinations for the offspring
random fertilization
fusion of maternal & paternal gametes to form a zygote is by chance
results in the zygote possessing a random possible genotype
spermatogenesis vs oogenesis
similarities: meiosis I & II; haploid daughter cells from diploid parent cells; multiplication, growth & maturation phases;
differences: 4 motile gametes vs 1 non-motile gamete & 3 polar bodies; testes vs ovaries; puberty until death vs fetus until menopause
gene
regions of DNA made up of nucleotides
unit of heredity
genome
all the genetic material in the chromosomes of an organism
genes & DNA sequences
genotype vs phenotype
genotype : combination of alleles which an organism has
phenotype : observable traits which an organism has
exons
coding regions of DNA
transcribed into mRNA & translated into proteins
introns
non-coding regions of DNA
spliced out of mRNA prior to translation
types of introns
centromere : point of attachment between sister chromatids & point of spindle fibre attachment
telomere : protective cap on the ends of chromosomes to prevent erosion & degradation during cell division
transcription
RNA polymerase synthesizes mRNA by copying DNA from 5’ to 3’ in the nucleus where uracil replaces thymine
translation
mRNA travels to a ribosome (rough endoplasmic reticulum or cytoplasm) where codons bind to anticodons on tRNA which bring amino acids that are joined by peptide bonds to form a functional protein (polypeptide)
gene expression
process by which genetic information is decoded to synthesize a functional gene product
can be regulated leading to cellular differentiation & specialization
transcription factors
proteins which regulate gene expression through inducing (activator) or inhibiting (repressor) RNA polymerase from attaching to the promoter region of a gene
translation factors
microRNA which binds to messengerRNA to prevent the process of translation
epigenetic factors
environmental influences which act as transcription factors that regulate gene expression by altering the accessibility of the DNA sequence from RNA polymerase
(how tightly/loosely DNA is wrapped around histones)
HOX gene
master regulatory gene that codes for transcription factors that regulate an organism’s morphology
SRY gene
codes for the SRY protein (transcription factor) which determines sex by promoting genes associated with testes formation & represses genes associated with female reproductive structures
(cell differentiation)
