4a (DNA RNA protein synthesis)

Question 1

DNA in eukaryotic cells

Answer 1

long, linear dna molecules
found in nucleus
found as chromosomes
wound around histones (protein)
has introns
mitochondria and chloroplasts in eukaryotic cells also have dna (similar to prokaryotic and found in matrix)

Question 2

DNA in prokaryotic cells

Answer 2

shorter, circular dna molecules
found in cytoplasm
found as coiled chromosomes or plasmids (plasmids can be passed between bacteria)
not associated with proteins (condenses to fit in the cell by supercoiling)
no introns

Question 3

what is a chromosome?

Answer 3

structure made of bundles of DNA tightly coiled around histones which add to stability.

Question 4

what is a gene?

Answer 4

sequence of DNA bases that codes for amino acid sequence of a polypeptide or functional RNA

Question 5

what is an allele?

Answer 5

version of a gene. order of bases in each is slightly diff so code for slightly diff versions of same polypeptide

Question 6

what is a homologous chromosome?

Answer 6

pair of matching chromosomes w same shape and size w same genes but could have diff alleles. alleles coding for same characteristic found at same fixed locus on each chromosomes in homologous pair

2 chromosomes that carry the same genes

Question 7

what is a genome?

Answer 7

organisms complete set of genes

Question 8

what is a proteome?

Answer 8

all the proteins that a cell is able to produce

Question 9

what is the genetic code?

Answer 9

sequence of base triplets (a codon) in mRNA which codes for specific amino acids to make polypeptide/ functional rna

Question 10

what is functional rna?

Answer 10

rna molecules that perform specific tasks during protein synthesis

Question 11

key features of dna

Answer 11

non-overlapping- base triplets are read in sequence, separate from triplet before and after and triplets dont share bases
degenerate- more poss combos of triplets than there are amino acids so some amino acids are coded for by more than one base triplet. some triplets tell cell when to start/ stop protein production
universal- same specific base triplets code for same amino acids in all living things

Question 12

what are introns?
what are exons?
what are non-coding multiple repeats?

Answer 12

non-coding parts of DNA
coding parts of DNA
non-coding regions of multiple base repeats between genes eg CCTTCCTTCCTT

Question 13

mRNA

Answer 13

single polynucleotide strand
uracil not thymine
sequence of 3 bases is called a codon
no hydrogen bonds- linear structure
no amino acid binding site (doesnt carry amino acids)
carries genetic code from DNA to ribosomes
made during transcription

Question 14

tRNA

Answer 14

single polynucleotide strand folded into clover shape
uracil not thymine
sequence of 3 bases is an anticodon
hydrogen bonds between specific base pairs hold molecule in clover shape
has amino acid binding site to carry amino acid
carries amino acids that are used to make proteins to the ribosomes
involved in translation

Question 15

what happens in transcription?

Answer 15

RNA polymerase attaches to DNA double helix at the beginning of gene (promotor region)
hydrogen bonds between DNA strands are broken and DNA uncoils into 2 strands exposing the bases
1 of the strands acts a s a template to make mRNA copy
RNA nucleotides align by complimentary base pairing and are joined together by RNA polymerase forming phosphodiester bonds and complimentary mRNA strand is produced (except T is replaced by U)
hydrogen bonds naturally reform
RNA polymerase reaches termination region and stops making mRNA
then splicing
then mRNA leaves nucleus

Question 16

what is splicing?

Answer 16

in transcription in eukaryotes, introns and exons are copied into mRNA
this is pre-mRNA
splicing occurs where introns are removed and exons are joined together resulting in mRNA which then leaves nucleus for translation

Question 17

what happens in translation?

Answer 17

mRNA attaches to ribosome at start codon
tRNA molecules carry amino acids to it
tRNA w anticodon complimentary to first codon on mRNA attaches to mRNA by specific base pairing 2nd trna attaches to next codon in same way
the 2 amino acids attached to trna join by peptide bond using energy from ATP
1st trna molecule moves away
3rd binds to next codon. this amino acid binds to first 2 and second trna moves away
continues until stop codon reached and polypeptide chain moves away from ribosome

Question 18

Hershey and chase

Question 19

how can the body make enough antibodies for all pathogens when theres only 206 genes?

Answer 19

206 genes each contain introns ad exons
exons can be alternatively spliced together
this produces a diff mRNA sequence
diff mRNA will therefore code for diff sequence of amino acids
this produces antibodies w diff secondary and tertiary structures

Question 20

how can a mutation result in the formation of a non-functional protein receptor?

Answer 20

change in DNA base sequence
change in amino acid sequence/ primary structure
alters position of hydrogen bonds
change in tertiary structure of receptor