DNA Review& Chromosomes

DNA StRucture• Rosalind Franklin-

Took first x-ray crystallography pictures of DNA

• Watson & Crick – used Franklin’s pictures to come up with double helical model of DNA

DNA is Genetic Material

• DEOXYRIBONUCLEIC ACID

– Controls protein production in cells

– Made up of many genes which control traits

DNA structure• Made up of units called

NUCLEOTIDES

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DNA structure

Remember that DNA has 2 strands

Each strand is COMPLEMENTARY to the other

Complementary Strands• If we know the DNA sequence of one

strand, we can predict the DNA sequence of it’s complement

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C C GG A AT T

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C

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A

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A

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T

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T

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G

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G

Review• Write the complementary strand

sequence for the following:

ATTCGACTACCTG

TAAGCTGATGGAC

Identify its pair

Cytosine pairs with: GUANINE

Adenine pairs with:

THYMINE

DNA Folding• DNA strands must fold up into a

smaller package before cellular division can occur.

• Histones are proteins that the DNA strand wraps around to form condensed packages.

• This complex of proteins and DNA is called chromatin.

• https://www.youtube.com/watch?v=gbSIBhFwQ4s

Chromosomes• These final

packages of condensed DNA are known as chromosomes.

To be Genetic Material• Requirements:

1. Able to store and pass information from one generation to the next

2. The stored info is responsible for traits

3. Must be easily replicated with minimal errors

Genes• DNA is the blueprint of

the body, because it tells the cells what proteins to make.

• A section of a chromosome with a particular sequence of DNA that codes for a specific protein(s) is called a gene.

• These proteins determine traits.

Alleles• Most genes have at least two

different proteins that can determine traits.

• Different sequences of DNA that code for different proteins of the same trait are called alleles.

TACTTGCATCGGTCAATCATGAACGTAGCCAGTTAG

TACTTGCCTGAATCAATCATGAACGGACTTAGTTAG

Blue eyesBrown eyes

Mutation• Alleles arise from genetic

mutation.

• A mutation is the change in the DNA sequence for a particular gene.

• There are two main types of mutations: – Point– Frame shift

Point Mutation• A point mutation is when a single

nucleotide of the sequence is miscopied during DNA replication.

TACGTTATAATC TACGTAATAATC

Substitution• The miscopy can cause a new

protein to be produced.

TACGTGATAATC

AUGCACUAUUAG

TACGTTATAATC

AUGCAAUAUUAG

Met-His-Tyr Met-Gln-Tyr

Silent Mutation• The miscopy can also have no

affect on the protein produced.

TACGTGATAATC

AUGCACUAUUAG

TACGTAATAATC

AUGCAUUAUUAG

Met-His-Tyr Met-His-Tyr

Frame shift• Frame shift is when the bases

shift and codons change.

• There are two types of frame shift– Deletion– Insertion

TAC GTG ATA ATC AC GTG ATA ATC ACG TGA TAA TC

TAC GTG ATA ATC A TAC GTG ATA ATC ATA CGT GAT AAT C

Insertion• Insertion is when a nucleotide is

put in the middle of the DNA sequence.

• This causes all the nucleotides to shift producing mostly new codons.

TAC GTG ATA ATC A TAC GTG ATA ATC ATA CGT GAT AAT C

Deletion• Deletion is when a nucleotide is

removed from the middle of the DNA sequence.

• Again this causes all the nucleotides to shift producing mostly new codons.

TAC GTG ATA ATC ACG TGA TAA TCAC GTG ATA ATC