DNA, Genes and Chromosomes

Question 1

do eukaryotes have introns?

Answer 1

yes

Question 2

do prokaryotes have introns?

Answer 2

no

Question 3

In mitochondria + chloroplasts in eukaryotic cells, DNA is…

Answer 3

• short
• circular
• not associated with proteins

Question 4

a chromosome is made up of…

Answer 4

DNA molecule associated with histone proteins

Question 5

when do chromosomes become visible?

Answer 5

prophase

Question 6

How is DNA packed into a chromosome?

Answer 6

1. DNA double helix
2. DNA + histones
3. DNA - histone complex coiled
4. Loops coil/pack together

Question 7

Give the definition of homologous pairs

Answer 7

pairs of chromosomes, 1 maternal and 1 paternal set. Contain the same genes in the same loci but are not genetically identical as they have different alleles

Question 8

what is the equation to remember the creation of a diploid cell from 2 haploids

Answer 8

n (23) + n (23) = 2n (46)

Question 9

definition of allele

Answer 9

alternative form of a gene

Question 10

characteristics of alleles?

Answer 10

• inherit/display at least 1 allele from either mum/dad
• when alleles same = code for same polypeptide
• alleles different = code for different poly.

Question 11

what is genotype and phenotype?

Answer 11

geno = genetic code 
pheno = characteristics (combination of proteins interacting with environment)

Question 12

definition of mutation

Answer 12

changes to the base sequence of a gene produces a new allele for that gene

Question 13

mutations can cause…

Answer 13

• a different polypeptide produced
• may not function properly or not at all
• i.e. if it was an enzyme, 3D active site changes shape, substrate no longer fits

Question 14

definition of a gene

Answer 14

base sequence of DNA that codes for:

• amino acid sequence of a polypeptide
• functional RNA

Question 15

definition of locus

Answer 15

a gene that occupies a fixed position in a particular DNA

Question 16

Definition of intron and exons

Answer 16

in = non-coding DNA 
ex = coding DNA (separated by 1 or more introns)

Question 17

1. there are __ naturally occurring amino acids.
2. _ bases code for _ amino acid = a _______
3. _ bases produce __ triplets = some amino acids are coded by more than 1 ____

Answer 17

1. 20
2. 3, 1 = triplet
3. 3, 64 = triplet

Question 18

definition of degenerate code

Answer 18

all but 2 amino acids are coded by more than 1 triplet

Question 19

definition of non-overlapping

Answer 19

each triplet is only read once

Question 20

definition of universal

Answer 20

each triplet codes for the same amino acid in all organisms

Question 21

definition of genome

Answer 21

complete set of genes in a cell (including mitochondria/chloroplasts)

Question 22

definition of a proteome

Answer 22

full range of proteins that can be produced by a cell

Question 23

definition of a codon

Answer 23

sequence of 3 bases on mRNA that codes for a single amino acid

Question 24

what is the shape of tRNA compared to mRNA?

Answer 24

t = folded clover leaf shape 
m = single helix

Question 25

tRNA and mRNA are both...

Answer 25

single stranded nucleotide chains

Question 26

which one is less chemically stable t or mRNA?

Answer 26

mRNA - broken down in a few days

Question 27

What is tRNA complementary to?

Answer 27

has complementary anticodons to the codons on the mRNA

Question 28

what is mRNA complementary to?

Answer 28

has complementary codons to the triplets on DNA

Question 29

Name the 2 steps of protein synthesis

Answer 29

1. transcription: production of mRNA (DNA transcribed into mRNA) 2. translation: production of poly. using sequence of codons. Occurs in ribosomes

Question 30

what does RNA helicase do?

Answer 30

- unwinds section of DNA (breaks hydrogen bonds) | - exposes the gene that needs to be transcribed

Question 31

what does RNA polymerase do?

Answer 31

- attaches to template strand | - joins complementary RNA molecules together

Question 32

What is formed in transcription?

Answer 32

pre-mRNA

Question 33

In prokaryotes transcription forms ______ not __-_____ as there are no ____ present. So _____ does not occur.

Answer 33

mRNA, pre-mRNA, introns, splicing

Question 34

What occurs only in eukaryotes?

Answer 34

splicing

Question 35

describe splicing

Answer 35

1. pre-RNA = introns + exons 2. introns prevent synthesis of poly. 3. base sequences corresponding to these introns removed 4. then replaced with functional exons

Question 36

how does mRNA leave the nucleus

Answer 36

via nuclear pores

Question 37

tRNA has a specific _______ and attaches to a specific amino acid via the amino acid ________ ___.

Answer 37

anticodon, attachment site

Question 38

does translation need energy?

Answer 38

yes - in the form of ATP hydrolysis

Question 39

definition of a polysome

Answer 39

- multiple ribosomes working simultaneously along a strand of mRNA, - increases rate of synthesis + protein yield

Question 40

Stages of translation: 1. mRNA associates with ribosome in ________ 2. first 2 codons on ribosome attract complementary ______ 3. ______ on tRNA join via __________ base pairing (forms ______ bonds with codons) 4. _____ bond formed between __ amino acids (catalysed by ______ transferase) 5. ribosomes move forward by 1 codon 6. first tRNA leaves ribosome, new one enters carrying 3rd codon 7. another ______ bond forms (between second and new amino acid) = forms _________ 8. ribosome moves along until reaching _____ codon and then detaches (presence of release ____) 9. _________ chain released ______ into correct shape

Answer 40

1. cytoplasm 2. tRNA 3. anticodons, complementary, hydrogen 4. peptide, 2, peptidyl 7. peptide, polypeptide 8. stop, factor 9. polypeptide, folding

Question 41

In prokaryotic cells: DNA molecules are _____, circular and not associated with ______.

Answer 41

short, proteins

Question 42

In the nucleus of eukaryotes: DNA molecules are very long, ______ and associated with proteins, called_____.

Answer 42

linear, histones

Question 43

what is the definition of a triplet?

Answer 43

A sequence of three DNA bases which codes for a | specific amino acid

Question 44

chromosomes have 2 _______ joined by the ________. The 2 ______ are identical copied

Answer 44

chromatids, centromere, chromatids

Question 45

how many chromosomes do humans have in each somatic cell?

Answer 45

46