genetics

Question 1

what are the types of DNA in cells ?

Answer 1

bounded linear DNA in nucleus (eukaryotic)

unbounded circular DNA in mitochondria/chloroplast (eukaryotic)

unbounded circular DNA in cytosol (prokaryotic)

Question 2

DNA structure

Answer 2

anti-parallel double helix

two complementary strands of nucleotides

5’ end & 3’ end nomenclature

Question 3

nucleotide

Answer 3

nitrogenous base

deoxyribose sugar

phosphate group

Question 4

bonds between DNA strands

Answer 4

weak hydrogen bonds between complementary base pairs

A & T : two hydrogen bonds

C & G : three hydrogen bonds

Question 5

helicase

Answer 5

unwinds DNA

breaks weak hydrogen bonds between DNA strands

exposes nucleotide bases

Question 6

polymerase

Answer 6

copies DNA

bonds complementary nucleotides from 5’ to 3’

proofreads new DNA strands

Question 7

homologous chromosomes

Answer 7

pair of maternal & paternal chromosomes which carry the same genes, but may vary in alleles

Question 8

independent assortment

Answer 8

homologous chromosomes line up & separate independently during metaphase I

results in random maternal & paternal chromosomal combinations

Question 9

crossing over

recombination

Answer 9

recombination of genes between non-sister chromatids of homologous chromosomes during prophase I

results in recombinant chromatids creating unique genetic combinations for the offspring

Question 10

random fertilization

Answer 10

fusion of maternal & paternal gametes to form a zygote is by chance

results in the zygote possessing a random possible genotype

Question 11

spermatogenesis vs oogenesis

Answer 11

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

Question 12

gene

Answer 12

regions of DNA made up of nucleotides

unit of heredity

Question 13

genome

Answer 13

all the genetic material in the chromosomes of an organism

genes & DNA sequences

Question 14

genotype vs phenotype

Answer 14

genotype : combination of alleles which an organism has

phenotype : observable traits which an organism has

Question 15

exons

Answer 15

coding regions of DNA

transcribed into mRNA & translated into proteins

Question 16

introns

Answer 16

non-coding regions of DNA

spliced out of mRNA prior to translation

Question 17

types of introns

Answer 17

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

Question 18

transcription

Answer 18

RNA polymerase synthesizes mRNA by copying DNA from 5’ to 3’ in the nucleus where uracil replaces thymine

Question 19

translation

Answer 19

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)

Question 20

gene expression

Answer 20

process by which genetic information is decoded to synthesize a functional gene product

can be regulated leading to cellular differentiation & specialization

Question 21

transcription factors

Answer 21

proteins which regulate gene expression through inducing (activator) or inhibiting (repressor) RNA polymerase from attaching to the promoter region of a gene

Question 22

translation factors

Answer 22

microRNA which binds to messengerRNA to prevent the process of translation

Question 23

epigenetic factors

Answer 23

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)

Question 24

HOX gene

Answer 24

master regulatory gene that codes for transcription factors that regulate an organism’s morphology

Question 25

SRY gene

Answer 25

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)