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biology year 1 > DNA,RNA and protein synthesis A > Flashcards

DNA,RNA and protein synthesis A Flashcards

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1
Q

what is the difference between the DNA stored in eukaryotes vs. prokaryotes

A

-Eukaryotic DNA= long,linear,associated with proteins called histones, tightly coiled into chromosomes
-Prokaryotic DNA= short, circular, not associated with histones

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2
Q

name the protein associated with DNA in a chromosome

A

histone

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3
Q

compare and contrast DNA in eukaryotic cells with DNA in prokaryotic cells

A

COMPARISONS
-nucleotide structure is identical
-nucleotides joined by phosphodiester bond
CONTRASTS
-eukaryotic DNA is longer
-eukaryotic DNA is linear and prokaryotic is circular
-eukaryotic DNA is associated with histones

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4
Q

mitochondria and chloroplasts also contain ……… DNA like prokaryotic cells

A

circular

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5
Q

what is a gene

A

section of DNA on a chromosome coding for one or more polypeptides

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6
Q

What is the nature of the genetic code

A

-triplet code= sequence of three bases codes for a specific amino acid
-degenerate= more than one triplet codes for a single amino acid
-universal= same triplets code for the same amino acids in all living organisms
-non-overlapping= each triplet is read in sequence and bases are not shared between triplets

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7
Q

what is an exon

A

exons are sequences of DNA within a gene that code for amino acids

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8
Q

what are introns

A

introns are DNA sequences within a gene that don’t code for amino acids

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9
Q

what are non-coding base sequences

A

-DNA that does not code for sequences of amino acids
-found between genes and at the end of chromosomes

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10
Q

what are non coding repeats

A

DNA sequences found outside of genes that repeat over and over

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11
Q

name two types of non-coding DNA

A

introns and repeats

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12
Q

what name is given to a sequence of three DNA bases that codes for an amino acid

A

a triplet

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13
Q

what is a genome

A

complete set of genes in a cell

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14
Q

what is a proteome

A

the full range of different proteins that a cell is able to produce at a given time

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15
Q

what are alleles

A

different version of the same gene

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16
Q

what is a homologous pair of chromosomes

A

same size chromosomes with same genes, but different
alleles

17
Q

describe how a gene is a code for the production of a polypeptide

A

-because base/nucleotide sequence
-in a triplet
-determines order/sequence of amino acid sequence

18
Q

describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule

A

-condensation reaction
-between phosphate and deoxyribose
-catalysed by DNA polymerase

19
Q

not all mutations in nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why

A

-triplets code for same amino acid
-occurs in introns/ non-coding sequence

20
Q

name the type of bond between complementary base pairs

A

hydrogen

21
Q

name the type of bond between adjacent nucleotides in a DNA strand

A

phosphodiester

22
Q

what does the m in mRNA stand for

A

messenger

23
Q

what is an mRNA codon

A

an mRNA codon is a sequence of three mRNA bases that codes for amino acid

24
Q

what does t in tRNA stand for

A

transfer

25
Q

what are the differences between mRNA and tRNA

A

mRNA
-single helix/straight
-longer
-contains no hydrogen bonds
tRNA
-folded into clover shape
-shorter
-contains hydrogen bonds

26
Q

what are the 2 stages of protein synthesis

A

1.transcription
2.translation

27
Q

what is transcription

A

-eukaryotes= transcribing DNA to pre-mRNA in the nucleus
-prokaryotes=transcribing DNA to mRNA in cytoplasm

28
Q

what is splicing

A

-happens in eukaryotes only as prokaryotes do not have introns
-introns are removed from pre-mRNA to form a strand of mRNA containing exons

29
Q

describe how mRNA is formed by transcription in eukaryotes

A

-hydrogen bonds between DNA bases break
-only one DNA strand acts as a template
-free RNA nucleotides align by complementary base pairing
-uracil is used in place of thymine
-RNA polymerase joins nucleotides
-by phosphodiester bonds
- pre-mRNA is spliced to form mRNA

30
Q

describe how mRNA is produced from an exposed template strand of DNA

A

-free RNA nucleotides form complementary base pairing
-phosphodiester bonds form
-by action of RNA polymerase

31
Q

in eukaryotic cells, the base sequence of mRNA might be different from the sequence of the pre-mRNA. explain why

A

-introns in pre-mRNA
-removal of sections of pre-mRNA/ splicing

32
Q

describe the role of DNA helicase in eukaryotic transcription

A

-breaks hydrogen bonds between the two DNA strands in a gene
-separates strands and allows DNA double helix to uncoil
-allowing one strand to be used as a template
-to produce complementary mRNA

33
Q

what is translation

A

-translating mRNA into a polypeptide
-happens at the ribosomes

34
Q

describe how a polypeptide is formed by translation of mRNA

A

-mRNA attaches to ribosomes
-tRNA anticodons bind to complementary mRNA codons
-tRNA brings a specific amino acid
-amino acids join by peptide bond
-amino acids join with the use of ATP
-tRNA released
-the ribosome moves along the mRNA to form the polypeptide

35
Q

describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation

A

-tRNA brings specific amino acid to ribosome
-anticodon on tRNA binds to codon on mRNA
-amino acids join by condensation reaction using ATP

36
Q

what is the role of ATP in translation

A

● Hydrolysis of ATP to ADP + Pi releases energy
● So amino acids join to tRNAs and peptide bonds form between amino acids

37
Q

what is the role of tRNA in translation

A

● Attaches to / transports a specific amino acid, in relation to its anticodon
● tRNA anticodon complementary base pairs to mRNA codon, forming hydrogen bonds
● 2 tRNAs bring amino acids together so peptide bond can form

38
Q

what are anticodons and where are they found

A

-sequences of three bases found at the end of tRNA molecules
-bind to complementary codons in mRNA

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