CHAPTER 12 DNA & RNA. Why do Animals not look the same?

CHAPTER 12DNA & RNA

Why do Animals not look the same?

12.1 DNA

12.2 Chromosomes and DNA Replication

12.3 RNA and Protein Synthesis

12.4 Mutations

12.5 Gene Regulation

Chapter 12

DNA and RNA

Griffith’s Experiment

AVERY AND DNA

Hershey-Chase Experiment

Learning OutcomesAfter this section, you should be able to:

• describe the basic unit of DNA – the nucleotide;

• state and apply the rule of complementary base pairing.

12.1 DNA

A cell contains a nucleus and in the nucleus are chromatin strands that are made up of proteins and deoxyribonucleic acid (DNA).

an animal cell nucleus with chromatin strands inside

DNA molecule

protein molecules

12.1 DNA

How is DNA organised inside the cell nucleus?

Each DNA molecule consists of two parallel strands twisted around each other to form a double helix.

During cell division, the chromatin threads coil more tightly to form chromosomes inside the cell nucleus.

A molecule of DNA is wrapped around proteins to form a single chromatin thread.

12.1 DNA

What is DNA?• A molecule that carries genetic information.

• It is made up of nucleotides.

• A nucleotide is made up of:

(1) a deoxyribose (sugar) molecule,

(2) a phosphate group, and

(3) a nitrogen-containing base

- adenine (A), thymine (T),

guanine (G), or cytosine (C).

12.1 DNA

Possible nucleotides that can be formed:

adenine nucleotide

thymine nucleotide

guanine nucleotide

cytosine nucleotide

bases

sugar-phosphate backbone

polynucleotide

These nucleotides can be joined together to form polynucleotides.

12.1 DNA

The DNA molecule is made of two anti-parallel polynucleotide strands. (The two strands run in opposite directions.)

The bases on one strand form bonds with the bases on the other strand according to the rule of base pairing.

12.1 DNA

Rule of base pairing• Adenine (A) bonds with thymine (T)

• Guanine (G) bonds with cytosine (C)

These pairs of bases are called complementary bases.

• Adenine (A) and thymine (T) are complementary bases. • Guanine (G) and cytosine (C) are complementary bases.

12.1 DNA

The two anti-parallel strands of the DNA molecule coil to form a double helix structure.

bases

sugar-phosphate backbone

coiling of DNA

the double helix structure of DNA

12.1 DNA

Checkpoint

2. State the complementary base pair to the strand shown below:

Answer:

1. DNA molecules found in the cell nucleus are compacted to form chromatin strands. Other than DNA, what other molecule is found in chromatin strands?

Answer: Protein molecules

12.1 DNA

3. State the ratio of:(1) adenine : thymine, and(2) guanine : cytosine

in the DNA of a cell.

Answer:

(1)1 : 1

(2)1 : 1

4. The strands in a DNA molecule are ___________. The strands coil together to form a ______ ______ structure.

anti-paralleldouble helix

12.1 DNA

12.1 DNA

• Text book Questions• Page 294• Q1-5

12.1 DNA



12.4 Mutations


Chapter 12

DNA and RNA

Chapter 12.2

Prokaryote vs Eukaryote

Chapter 12.2

Nucleosomes

Chapter 12.2

DNA Replication

Review

• According to Chargaff's rule, the following proportion exists in DNA.

• A)C=G• B)C»T• C)C»G• D)C=T

Chapter 12.2

ReviewAll of the following were outcomes of Avery's experiment

on "the active principle" exceptA)the array of the elements of purified principle agreed

closely with DNA and the principle centrifuged to the same level as DNA.

B)protein digesting enzymes did not affect the sampleC)the extraction of lipids and proteins from the principle

only slightly reduced its activityD)DNA-digesting enzyme, DNase, destroyed all

transcription activity.

Chapter 12.2

ReviewThe fact that some viruses use DNA to direct their heredity was

demonstrated byA)finding radioactive sulfur from a bacteriophage in a

bacterium.B)finding radioactive phosphorus from a bacterium in a

bacteriophage.C)finding that radioactive phosphorus from a bacteriophage had

mutated in bacterium.D)finding radioactive phosphorus from a bacteriophage in a

bacterium.E)finding radioactive sulfur from a bacterium in a bacteriophage.

Chapter 12.2

ReviewIn DNA guanine always pairs withA)AdenineB)CytosineC)GuanineD)ThymineE)Uracil

Chapter 12.2

ReviewWith few exceptions, all nuclei of eukaryotes containA)genes to specify the portion of the organism in which

they are foundB)all the information needed for growing the whole

organismC)all of the chromosomes except sex chromosomes

which are restricted to sex organsD)single stranded DNAE)only euchromatin except in the case of the Y-

chromosome

Chapter 12.2

Review

In DNA, thymine always pairs withA)AdenineB)CytosineC)GuanineD)ThymineE)Uracil

Chapter 12.2

ReviewEach unit of a nucleic acid consisting of a sugar,

attached phosphate group, and base is aA)NucleolusB)NucleotideC)NucleosomeD)HistoneE)Genetisome

Chapter 12.2

ReviewA DNA molecule has the same amount of adenine and

thymine.A)TrueB)False

Chapter 12.2

ReviewIn the DNA molecule:A)adenine pairs with thymineB)guanine pairs with thymineC)cytosine pairs with thymineD)adenine pairs with cytosineE)All of the above are possible.A DNA molecule has the

same amount of adenine and thymine.

Chapter 12.2

Review

If one side of a DNA molecule contains the following sequence of nucleotides, AGTCCG, the complementary sequence on the other side would be:

A)GCCTGAB)AGTCCGC)TCAGGCD)CTGAATE)none of the above

Chapter 12.2

ReviewDuring your summer job at Virotech, you isolate a

previously unknown virus. Analysis of its genome reveals that it is composed of a double stranded DNA molecule containing 14% T (thymine). Based on this information, what would you predict the %C (cytosine) to be?

A)14%B)28%C)36%D)72%E)Cannot be determined from the information given.

Chapter 12.2

ReviewText book questions page 2991-6

Chapter 12.2

12.1 DNA



12.4 Mutations


Chapter 12

DNA and RNA

How are proteins made?


• Types of RNA

Chapter 12

DNA and RNA

It is a temporary molecule that is made when needed.

It is a permanent molecule in the nucleus.

It is a small soluble molecule.It is a large insoluble molecule.

No fixed ratio between A and U and between G and C.

Ratio of A:T and G:C is 1:1.

Nitrogen-containing bases are adenine (A), uracil (U), guanine (G) and cytosine (C).

Nitrogen-containing bases are adenine (A), thymine (T), guanine (G) and cytosine (C).

Sugar unit is ribose.Sugar unit is deoxyribose.RNADNA (double helix)

DNA vs. RNA

17.2 Genes

• The DNA template is first transcribed into a messenger RNA (mRNA) molecule through a process called transcription.

• Transcription occurs in the nucleus of the cell. During transcription, the DNA codons in the gene are converted into RNA codons.

• The mRNA molecule is then translated into polypeptides through the process of translation.

• Translation occurs in the cytoplasm of the cell.



DNA template

transcription

mRNA - RNA contains

uracil (U) instead of thymine (T)

polypeptide

translation

17.2 Genes

• The DNA template is first transcribed into a messenger RNA (mRNA) molecule through a process called transcription.

• Transcription occurs in the nucleus of the cell. During transcription, the DNA codons in the gene are converted into RNA codons.

• The mRNA molecule is then translated into polypeptides through the process of translation.

• Translation occurs in the cytoplasm of the cell.



17.2

Transcription and Translation

Genes

1

2

template strand gene unzips

transcription

ribosome

mRNA

mRNA molecule

3 attachment to ribosome

Translation• Attachment of the mRNA to a ribosome is the start of the

translation process.

• The codons on the mRNA tells the cell what amino acids to attach together and in what order.

peptide bondamino acids attached to tRNA

ribosome

codon

17.2 Genes

• Attachment of mRNA with ribosome• mRNA is then read by codons (every 3 bases)• Bases found on mRNA will be complementary to tRNA

(transfer) bases.• Thus, formation of polypeptide chain begins with

bonding of other tRNA (different amino acids).• Polypeptide chain elongates with reading of every 3

bases on mRNA by ribosome.• It will elongate till it reaches the termination codon found

on mRNA. • Once completed, ribosome shall release mRNA and

protein is released into cytoplasm for processing.

RNA Editing

The Genetic Code

Review

• Text Book• Page 306• Question 1-5

12.4 Mutations

12.4 Point Mutations

12.4 Frame Shift Mutations

12.4 Chromosome Mutations

Review

• Text book• Page 308• Question 1-4

12.5 Differentiation

12.5 Hox genes

• Any of the developmental control genes involved in making and identity of each body segment. Mainly during early embryonic development.

12.5 Hox genes

Review

• Text book • Page 312• Questions 1-5

REMINDER

• Nucleotide

Learning OutcomesAfter this section, you should be able to:

• state that DNA molecules contain the genetic code;

• state what is meant by the genetic code;

• state that a gene is a specific sequence of nucleotides in a DNA molecule that controls the production of a polypeptide.

12.2 Genes

• The Eye Colour is Green due to proteins.• Proteins are formed thanks to genes found

in the DNA that encodes for eye colour.• Over time, eye colour may change (either

lighten or darken)• This is due to different expressions of the

gene which leads to different release of proteins thus a different colour!

What is a gene?

• It is a segment of DNA.

• The nucleotide sequence in the gene determines the protein formed thus the hereditary trait.

• Since there are four different nucleotides, for a gene made up of n nucleotides, there are 4n different combinations of nucleotides.

gene

DNA

polypeptide coded by the gene

17.2 Genes

• Three nucleotides in a gene form a codon and each codon codes for one amino acid.

• The genetic code states which amino acid each codon codes for.

Example:Codon(DNA)

Amino acid coded for

TAC Methionine (M)TAT Alanine (A)CAT Lysine (K)GAG Glutamic acid (E)ACA Serine (S)

17.2 Genes

• How are proteins made?

CHAPTER 12 DNA & RNA. Why do Animals not look the same?

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