3.4.1 DNA, genes and chromosomes (Unit 4 DNA and Relationships) Flashcards

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1
Q

What is a gene?

A

A gene is a section of DNA that contains the coded information for making polypeptides and functional RNA.

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2
Q

What is the locus?

A

A locus is the position of a gene on a chromosome

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3
Q

What factors determine the phenotype and development of all organisms?

A

Genes and environmental factors

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4
Q

The genetic code uses 4 different DNA bases. What is the maximum number of different DNA triplets that can be made from these 4 bases?

A

4^3 = 64

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5
Q

What are some of the features of genetic code?

A

•It’s degenerative •It’s non-overlapping (each base only ready once) •It’s universal

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6
Q

Why is genetic code described as “degenerative”?

A

As one amino acid can be coded for by more than one triplet

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7
Q

Why is the genetic code described as being “universal”?

A

In all organisms the same triplet codes for the same amino acid;

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8
Q

What are exons?

A

Sequence that codes for amino acids.

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9
Q

What are introns?

A

Non-coding sequences (they at IN between genes)

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10
Q

Why is the genetic code described as “non-overlapping”?

A

Each base in the sequence is only read once

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11
Q

Describe the DNA in prokaryotic cells

A

•DNA molecules are shorter •They form a circle •They aren’t associated with proteins (histones) •NO chromosomes

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12
Q

Describe the DNA in eukaryotic cells

A

•DNA molecules are longer •They form a line (linear) •They occur in association with proteins called HISTONES to form chromosomes

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13
Q

What is an allele?

A

Different form of a gene

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14
Q

Explain why the DNA base sequences of homologous chromosomes are almost the same.

A

Homologous chromosomes have the same genes At the same loci Different alleles (different forms of the same gene) usually only have a small difference in their base sequence
They are the same size and the same shape

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15
Q

What name is given to the different forms of a gene?

A

Allele

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16
Q

Which 2 biological molecules make up a ribosome?

A

ribosomal RNA (rRNA) and Amino acids

17
Q

Describe the shape of a replicated chromosome

A

2 sister chromatids held together by centromere

18
Q

what is this a picture of?

A

Nucleotide

19
Q

Identify the blue circle in this nucleotide

A

phosphate

20
Q

Identify the green shape in this nucleotide

A

deoxyribose (pentose sugar)

21
Q

Indentify the pink rectangle in this nucelotide

A

organic base - either A T G or C

22
Q

If there is 18% adenine in a DNA sample what % will be thymine?

A

18

23
Q

If there is 18% adenine in a DNA sample what % will be guanine?

A

32

24
Q

name the enzyme involved in DNA replication

A

Helicase AND DNA polymerase

25
Q

What is a homologous pair of chromosomes?

A

2 chromosomes that are the same size and shape and carry the SAME genes but different alleles

26
Q

What is a bivalent?

A

Two homologous chromosomes that pair up during meiosis, they are joined during crossing over

27
Q

What is a chiasmata?

A

The point where a bivalent crosses over