Mutation

A change in DNA

Genetic variation

Differences in genes and traits within a population

What can cause mutations?

UV radiation, radiation, chemicals, high temperatures, and low temperatures

Can mutations be beneficial, neutral, or harmful?

Yes, mutations can be beneficial, neutral, or harmful

Crossing over

The exchange of genetic material between homologous chromosomes during meiosis

Why is genetic variation important?

It allows organisms to have different traits that may help them survive changes in their environment

Where does a lot of genetic variation come from?

Sexual reproduction, because genetic information from two parents is combined

Dominant allele

An allele that is expressed when at least one copy is present

Recessive allele

An allele that is usually expressed when two copies are present

Homozygous

Having two of the same alleles

Heterozygous

Having two different alleles

Genotype

The genetic combination of alleles an organism has

Phenotype

The physical or observable trait

Incomplete dominance

When neither allele completely dominates and the heterozygous phenotype is intermediate

Example of incomplete dominance

Red and white snapdragons can produce pink flowers

RR in snapdragons

Red flowers

rr in snapdragons

White flowers

Rr in snapdragons

Pink flowers

Rr × Rr

25% red, 50% pink, and 25% white

Codominance

When both alleles are expressed at the same time

Example of codominance

AB blood type

What are the main ABO blood types?

A, B, AB, and O

What determines positive or negative blood type?

The presence or absence of the Rh factor

Universal red blood cell donor

O negative

Universal red blood cell recipient

AB positive

Gregor Mendel

The father of genetics who studied pea plants

Law of Segregation

The two alleles for a gene separate during gamete formation, so each gamete receives one allele

When does segregation happen?

During meiosis or gamete formation

Law of Independent Assortment

Different gene pairs can be inherited independently of one another

How many chromosomes do humans normally have?

46

How many autosomes do humans have?

44

How many sex chromosomes do humans have?

2

Typical female sex chromosomes

XX

Typical male sex chromosomes

XY

What sex chromosome can the mother contribute?

X

What sex chromosome can the father contribute?

X or Y

Chance of an XX or XY combination

Approximately 50% each

Why are some X-linked recessive traits more common in males?

Males usually have only one X chromosome, so a recessive allele on that X chromosome can be expressed

How can a recessive trait appear to skip a generation?

A recessive allele can be carried by a parent without being expressed and then passed to a child

DNA

The molecule that contains genetic instructions for an organism

What shape is DNA?

A double helix

What makes up the outside of DNA?

Sugar and phosphate

What sugar is found in DNA?

Deoxyribose

What are the four DNA bases?

Adenine, thymine, cytosine, and guanine

DNA base-pairing rule

A pairs with T, and C pairs with G

Gene

A section of DNA that contains instructions for a specific product, usually a protein

What determines the information stored in DNA?

The order of the base pairs

What are proteins made of?

Amino acids

Enzymatic proteins

Proteins that help with chemical reactions

Hormonal proteins

Proteins involved in communication and regulation of growth and development

Structural proteins

Proteins that help make up the physical structure of cells and tissues

Gene expression

Using information in DNA to make products, especially proteins

Transcription

The process of making RNA from DNA

What is produced during transcription?

mRNA

mRNA

Messenger RNA that carries genetic instructions from DNA to the ribosome

Translation

The process of using mRNA instructions to build a protein

Where does translation happen?

At the ribosome

What does a ribosome read?

mRNA

Codon

A group of three bases on mRNA

What does a codon specify?

An amino acid

tRNA

Brings amino acids to the ribosome

What happens to amino acids during translation?

They are linked together to form a protein

Ribosome

A cellular structure that reads mRNA and helps build proteins

DNA vs RNA

DNA is double stranded while RNA is usually single stranded

DNA sugar

Deoxyribose

RNA sugar

Ribose

What base does RNA use instead of thymine?

Uracil

DNA bases

A, T, C, G

RNA bases

A, U, C, G

Golgi apparatus

Modifies, packages, stores, and directs proteins

Protease

An enzyme that breaks down proteins

Amylase

An enzyme that breaks down carbohydrates

Where is amylase produced?

Salivary glands and other parts of the digestive system

What does protease break down?

Proteins

What does amylase break down?

Carbohydrates

Gene regulation

Controls which genes are turned on or off and how much they are used

Why is gene regulation important?

It allows different cells to use different genes and make different proteins

Do all cells use all of their genes at the same time?

No

Why can cells have different functions even though they contain the same DNA?

Different cells turn different genes on and off

What does gene regulation control?

Which proteins are made, when they are made, and how much is made

What is the big picture of gene expression?

DNA → RNA → Protein → Cell functions and traits