Chapter 9 DNA: The molecule of heredity

• What is heredity?• What does DNA have to do with heredity?• What is DNA?• What is a chromosome?• What is a gene?• What is the relationship between chromosomes,

DNA and genes? • What is a genome?• How is DNA inherited?• Why is it important to know about DNA?

I. DNA - the "molecule of heredity"

• A. DNA—the genetic information of all living organisms

• B. Genetic information units are called genes1.Gene—a length of DNA containing

information to make a protein

What is heredity?

• The genetic transmission of characteristics from parent to offspring

• Parent cells to offspring cells

• Parent organisms to offspring organisms

What does DNA have to do with heredity?

• DNA encodes information which results in your characteristics

• Offspring (cells and organisms) receive DNA from their parents

What is DNA?

• Two polymers of nucleotides which interact via complementary base pairing

What is DNA?

1953 – James Watson & Francis Crick model DNA structure as a double helix

What is a chromosome?

• Chromosomes contain DNA and associated proteins (which allow the DNA to condense/wind up tightly)

What is a chromosome?

• Tightly packed DNA wrapped around histone proteins

What is a chromosome?

What is a gene?

• A sequence of DNA nucleotides which encodes information for a cell to make a specific protein

• Example: CFTR gene

What is the relationship between chromosomes, DNA, and genes?

gengenee

gengenee genegene

Chromosomes contain DNA

Genes are sequences of DNA nucleotides

Genes are located on chromosomes

What is a genome?

• All the DNA found in a species

The Human Genome

• 46 chromosomes • (23 pairs)

• ~30,000 genes

Human Genome Project

• -Sequenced the human genome

• -Mapped all human genes

GeneMap linkChromosome viewer

1. DNA contains hundreds of chromosomes which are composed of genes.

2. A chromosome contains hundreds of genes which are composed of DNA.

3. A gene contains hundreds of chromosomes which are composed of DNA.

4. DNA contains hundreds of genes which are composed of chromosomes.

What is the relationship among DNA, a gene, and a chromosome?

Which of the following represents proper complementary base pairing in

DNA? 1) Adenine with guanine; cytosine with thymine

2) Thymine with thymine; cytosine with cytosine

3) Adenine with cytosine; guanine with thymine

4) Adenine with thymine; guanine with cytosine

5) None of the above

The DNA of an organism contains 20 percent cytosine nucleotides. What percentage of its bases would be

guanine? 1)10 percent2)20 percent3)30 percent4)40 percent5)80 percent6)It cannot be determined•  

How is DNA inherited?

• DNA is replicated (copied) prior to cell division

• Each cell “inherits” a copy of each replicated chromosome

DNA replication results in “double stranded”

chromosomes

How is DNA inherited?

• DNA replication is followed by cell division

DNA replication is semi-conservative

DNA replication animation

Why is knowledge of DNA important?

• DNA is involved in most, if not all characteristics

• DNA can change

• Changes in DNA can result in disease

• Understanding genes involved in disease can lead to prevention and treatment of disease

DNA polymerase and point mutations

• 1 mistake made every 10,000 replicated nucleotides

Repair enzymes limit mutations to 1 in a billion replicated nucleotides

Uncorrected replication errors may result in genetic disorders & diseases

Gene mutation & deafness

Obesity research in mice

Personal decisions can result in greater/lesser frequency of point mutations

Why are there mutations?

• For evolutionists:• Since mutations result in serious

disorders, why has evolution not perfected a DNA polymerase that does not make mistakes?

• For creationists:• Since mutations result in serious

disorders, why would an all knowing, loving God design us with an imperfect DNA polymerase that makes mistakes?

Mutations are a source of genetic diversity

• Phenotypic variation (diversity) is based on genetic variation

Mutations are a source of genetic diversity

Genetic variation and community interactions

A length of DNA containing information to make a protein is called1)a chromosome2)An exon3)A gene4)DNA helicase5)a nucleotide

Replication of the DNA sequence, GATTAC would produce the

sequence1)GATTAC

2)CATTAG

3)CTAATG

4)AGCCGA

5)None of these

1. each new DNA molecule contains two new single DNA strands.

2. some mistakes are made during DNA replication.

3. certain nucleotides pair with other specific nucleotides.

4. Each DNA molecule produced consists of one parental DNA strand and one newly synthesized strand.

5. Only half the chromosomes are copied during replication.

Semiconservative replication refers to the fact that

The enzyme that replicates DNA by catalyzing the dehydration synthesis of individual

nucleotides is• 1) DNA replicase• 2) DNA synthetase• 3) DNA polymerase• 4) Nucleotidase• 5) DNA helicase

A random change in a nucleotide of DNA

1)is always harmful to the organism2)is always corrected by repair enzymes3)will kill the organism in which it occurs4)is never beneficial to the organism5)can occur during DNA replication