3.4.1 DNA, genes + chromosomes

Question 1

describe DNA in prokaryotes

Answer 1

DNA molecules are short and circular
found in circular plasmids and circular chromosomes
don’t have nuclei, mitochondria and chloroplasts

Question 2

describe DNA in eukaryotes

Answer 2

DNA molecules are long, linear and found in the nucleus. DNA molecules are associated with proteins (histones)
DNA has a negative charge, histones have a positive charge= DNA winds around the histone and creates an ionic bond
DNA and histone condenses into a chromosome

Question 3

how many chromosomes are found in one cell

Answer 3

46 (23 pairs)

Question 4

describe DNA in mitochondria and chloroplasts

Answer 4

DNA is short and circular like plasmids found in eukaryotes
chloroplasts and mitochondria have circular DNA have origins of bacteria

Question 5

describe the differences between the structure and organisation of DNA in prokaryotes and eukaryotes

Answer 5

prokaryotes have circular and short DNA whereas eukaryotes have long and linear DNA
prokaryote DNA is found in circular chromosomes and circular plasma whereas eukaryotes DNA found in the nucleus
DNA in prokaryotes is associated with histones whereas DNA and prokaryote is not

Question 6

describe the similarities between the structure and organisation of nuclear DNA in eukaryotes and prokaryotes

Answer 6

both:
contain phosphodiester bonds
made up of DNA nucleotides
have negatively charged DNA
have double stranded DNA

Question 7

definition of gene

Answer 7

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

Question 8

definition of locus

Answer 8

a fixed position of a chromosome where a gene is found

Question 9

definition of allele

Answer 9

different version of the same gene

Question 10

definition of genome

Answer 10

the entire genetic material in an organism/ cell

Question 11

definition of introns

Answer 11

non coding regions of a gene

Question 12

definition of exons

Answer 12

part of a gene that contain instructions for making many proteins

Question 13

features of chromosomes

Answer 13

exist in homologous pairs and carry the same genes as eachother

Question 14

what does. a gene contain

Answer 14

a sequence of DNA bases which determine a specific amino acid sequence

Question 15

how are bases read in genetic code

Answer 15

triplets which correspond to one amino acid

Question 16

how do you read a genetic code table

Answer 16

look down side for the first letter in the triplet, then look along the top for the second letter in the triplet and then find the triplet with the correct third letter

Question 17

what are the 3 properties of genetic code

Answer 17

universal
non- overlapping
degenerate

Question 18

what does universal mean

Answer 18

genetic code is the same in every living organism

Question 19

what does non- overlapping mean

Answer 19

each base / triplet is read only once, assigns an amino acid and moves on

Question 20

what does degenerate mean

Answer 20

multiple triplets code for the same amino acid

Question 21

why is the feature of genetic code being degenerate helpful

Answer 21

if there is a mutation that he amino acids would usually stay the same and protein isn’t affected

Question 22

how can a mutation be harmful to the primary structure of a protein

Answer 22

changes the R group of amino acids so the structure can change and for different bonds
charges of amino acids may differ and shape of protein will change

Question 23

what does TAG mean in genetic coding

Answer 23

stop converting code into amino acids

Question 24

what is the name for non coding sections of a gene

Answer 24

introns

Question 25

what is the enzyme that breaks hydrogen bonds to unwind DNA double helix during transcription

Answer 25

RNA polymerase

Question 26

what is the process of transcription

Answer 26

1. hydrogen bonds are broken, unwinding DNA using RNA polymerase and exposes DNA bases
2. free floating RNA nucleotides line up against adjacent complimentary base pairs
3. RNA polymerase creates phosphodiester bonds between adjacent RNA nucleotides (making pre mRNA)
4. eukaryotes remove introns from pre-mRNA to make mature mRNA (through splicing)

Question 27

how does DNA move to ribosomes

Answer 27

a copy of each gene is sent there as DNA is too large (mRNA)

Question 28

what happens during transcription

Answer 28

a base sequence in a gene is used to create a short single stranded piece of RNA (mRNA)

Question 29

what are the differences in structure between DNA and mRNA

Answer 29

DNA- long strand mRNA- short strand
DNA- double stranded mRNA- single stranded
DNA- deoxyribose mRNA- ribose
DNA- thymine mRNA- uracil
DNA- hydrogen bonds mRNA- no hydrogen bonds

Question 30

how many tRNA molecules are in each cell

Answer 30

64

Question 31

what is the role of tRNA

Answer 31

transport amino acids to ribosomes

Question 32

what is the structure of tRNA

Answer 32

single stranded
clover leaf shape
amino acid binding site
anticodon

Question 33

what is the anticodon complimentary to

Answer 33

codons on mRNA

Question 34

what are the similarities between mRNA and tRNA

Answer 34

both are:
single stranded
temporary
same bases
ribose sugar
phosphodiester bonds
found in ribosome

Question 35

what are the differences between mRNA and tRNA

Answer 35

m- linear t- clover leaf
m- codons t- anticodons
m- nucleus t- ribosomes

Question 36

what is the process of translation

Answer 36

1. mRNA binds to ribosome
2. 2 tRNAs arrive at ribosome carrying specific amino acids, hydrogen bonds form between codons and complimentary anticodons
3. a peptide bond forms between amino acid in a condensation reaction, using ATP
4. 1 tRNA leaves, ribosome moves to next codon
5. the next tRNA binds to codon, another peptide bond forms between amino acids
6. steps repeat until tRNA reaches a stop codon, a long sequence of amino acids form and detaches to form a polypeptide