AQA AS Biology 7401- 3.4- Topic 8 DNA, Gene and Protein Synthesis

Frage 1 von 24

1

what is a gene

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a gene is a section of DNA that contains the coded information for making polypeptides and functional RNA.
a gene is a long chain of DNA
a gene is a part of chromosome
a gene is a link in DNA

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Frage 2 von 24

1

what is a locus

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a section of DNA located at a particular position
an allele
the environmental factors that determine the nature and development of all organisms

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Frage 3 von 24

2

what does the DNA base sequence code for

Wähle eine oder mehr der folgenden:

the amino acid sequence of a polypeptide
a functional RNA
mutations
DNA codes for mRNA and tRNA

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Frage 4 von 24

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in trying to discover how DNA bases coded for amino acids, scientists suggested that there must be a minimum of three bases that coded for each amino acid. their reasoning was as follows:

Only ❌ different amino acids regularly occur in proteins
Each amino acid must have its own code of bases on the DNA
Only ❌ different bases are present in DNA
If each base coded for a different amino acid, only four different amino acids could be coded for
Using a pair of bases ❌ are possible, which is ❌
Three bases produce ❌, ❌ enough to satisfy the requirement of ❌

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20

four

16 (4^2) different codes

still inadequate

satisfactory to the requirement

64 (4^3) different codes

more than

this is not

20 amino acids

four different amino acids

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Frage 5 von 24

1

what is a triplet

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a set of three bases that codes for an amino acid
three daughter cells produced by meiosis
three portions of DNA

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Frage 6 von 24

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further experiments have revealed the following features of the gentic code:

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a few amino acids are coded for by only a single triplet
the remaining amino acids are coded for by between two and six triplets each
a triplet is read various directions along the dna strand
the code is known as degenerate code because most amino acids are coded for by more than one triplet
a triplet is always read in one particular direction along the dna strand
the start of a dna sequence that codes for a polypeptide is always the same triplet. this codes for the amino acid methionine, if this methionine molecule does not form part of the final polypeptide, it is later removed
three triplets do not code for any amino acid. these are called stop codons and mark the end of a polypeptide chain. they act in much the same way as a full stop at the end of a sentence
the code is non-overlapping, in other words each base in the sequence is read only once. thus six bases numbered 123456 are read as triplets 123 456, rather than triplets 123 234 345 456
the code is universal, with a few minor exceptions each triplet codes for the same amino acid in all organisms. this is indirect evidence for evolution
one amino acid codes for only a single triplet
the code is known as non-degenerate code because most amino acids are coded for only one triplet

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Frage 7 von 24

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even within genes, only certain sequences code for amino acids. these coding sequences are called . within the gene these are seperated by further non-coding sequences called .

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Frage 8 von 24

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in ( prokaryotic, eukaryotic ) cells, such as bacteria, the dna molecules are ( shorter, longer ), form a ( circle, square, line ) and are ( not associated, associated ) with protein molecules. ( Prokaryotic, Eukaryotic ) cells therefore ( do not, do ) have chromosomes.

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Frage 9 von 24

9

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in ( Eukaryotic, Prokaryotic ) cells, the DNA molecules are ( longer, shorter ), form a ( line rather than a circle, circle rather than a line ) and occur ( in association, not in association ) with proteins called ( histones, centromere ) to form structures called ( chromosomes, chromatids ). the mitochondria and chloroplasts of ( Eukaryotic, Prokaryotic ) cells also contain DNA which, like the DNA of ( Prokaryotic, Eukaryotic ) cells, is ( short, circular, long, square ) and no associated with proteins.

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Frage 10 von 24

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chromosomes are visible during the whole cell cycle

Wähle eins der folgenden:

WAHR
FALSCH

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Frage 11 von 24

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each thread on a chromosome is called a

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Frage 12 von 24

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the DNA in chromosomes is held together by

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Frage 13 von 24

9

How is DNA packed into chromosomes

Ziehe eine Antwort zum richtigen orangen Punkt.

DNA double helix

DNA molecule

DNA combined with histones

DNA-histone complex is coiled

Coils fold to form loops

loops coil and pack together

chromosome

DNA

Histone molecules

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Frage 14 von 24

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❌ produced ❌, such as ❌, are the result of the ❌ of a ❌ and an egg, each of which contributes ❌ complete ❌ of chromosomes to the offspring.

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sexually

asexually

organisms

bacteria

humans

mule

fusion

divison

sperm

egg

one

two

three

four

five

six

ten

a hundred and twenty

a hundred

set

sets

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Frage 15 von 24

1

a homologous pair is always two chromosomes that carry the same genes but not necessarily the same alleles of the genes

Wähle eins der folgenden:

WAHR
FALSCH

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Frage 16 von 24

1

what is an allele

Wähle eine der folgenden:

an allele is one of a number of alternative forms of a gene
an allele is a section of DNA that contains the coded information for making polypeptides and functional RNA

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Frage 17 von 24

1

if an allele is different, why is this?

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each allele has a different base sequence, therefore a different amino acid sequence, so produces a different polypeptide
each allele started off as one polypeptide chain but due to mutations, the alleles have changed and matured into a different allele

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Frage 18 von 24

1

where is eukarytoic DNA stored

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nucleus
floating in cytoplasm

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Frage 19 von 24

1

the synthesis of proteins takes place in cytoplasm. how is it possible for the DNA to be transferred so it can be translated?

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sections of DNA are transcribed onto a single stranded molecule called ribonucleic acid
sections of DNA are transcribed onto a single stranded molecule called rebonucleic acid
sections of DNA are transcribed onto a single stranded molecule called transfer ribonucleic acid

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Frage 20 von 24

4

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what are the two types of RNA?
RNA (RNA)
RNA (RNA)

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Frage 21 von 24

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the term ❌ refers to the ❌ of ❌ bases on ❌ that codes for a single amino acid

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codon

genome

proteome

sequence

direction

three

two

tree

mRNA

tRNA

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Frage 22 von 24

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( genome, codon, proteome )- the ( complete, incomplete ) set of ( genes, alleles ) in a cell, including those in mitochondria and/or chloroplasts

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Frage 23 von 24

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❌- the ❌ range of proteins produced by the genome. this is sometimes called the complete proteome, in which case the term proteome refers to the ❌ produced by a given type of cell under a certain set of conditions

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proteome

codon

genome

full

incomplete

proteins

enzymes

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Frage 24 von 24

3

RNA is made up of repeating mono nucleotide sub-units. it forms a single strand in which each nucleotide is made up of:

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pentose sugar: ribose
organic bases: adenine, guanine, cytosine, uracil
a phosphate group
pentose sugar: deoxyribose
organic bases: thymine, adenine, guanine, cytosine
a glycerol group

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