Genetics

DNAMitosis and Meiosis

What is DNA?

DNA RNA Proteins• DNA: stored in nucleus; holds

information on making everything• Does not leave nucleus!

• RNA: carries information from DNA in nucleus to other areas

• Proteins: Help with cell processes (making energy, breaking down waste) gives traits to organism (hair color, skin texture, etc.)

DNA RNA• Transcription: makes mRNA from DNA• Occurs in the nucleus of eukaryotic cells

• Why? DNA can’t leave nucleus!• mRNA is complementary to the DNA

Thymine(Uracil) = AdenineCytosine = Guanine

DNA: TAC GAT TAC CGG GTA ACT ATA TCAmRNA: AUG CUA AUG GCC CAU UGA UAU AGU

RNA Proteins• Translation: Makes proteins from mRNA• Ribosomes read instructions on mRNA;

find correct amino acids to build proteinmRNA: AUG CUAAA: Methionine Leucine

How is DNA organized?• DNA is coiled into chromosomes before

mitosis and meiosis• A normal human has 23 pairs or 46 total

chromosomes• Each chromosome contains different

genes with information on how to create every protein needed to make a human

What is Mitosis?• Mitosis: Cell Division to create identical

copies of cells• Occurs to replace dead cells or grow

existing tissues• Result: Two identical cells• Four main phases: Prophase, Metaphase,

Anaphase, Telophase• Remember: PMAT

• FIRST: DNA Replicates• Prophase: Prepare by

condensing chromosomes, breaking down nucleus

• Metaphase: Chromosomes line up in the middle of the cell

• Anaphase: Chromosomes move apart

• Telophase: Two identical cells form

What is Mitosis?

What is Meiosis?• Meiosis: Creates gametes used for

reproduction (eggs/sperm)• Cells have half the number of

chromosomes as beginning cell• Result: Four gamete cells• Same phases as mitosis but they occur

twice

What is Meiosis?• First: DNA Replicates• PMAT I phases• DNA replication

does not occur again• PMAT II phases• Result: Four

different gametes with half normal number of chromosomes

• Why is this necessary?

Practice• Fill in the chart with the necessary

information.Mitosis Meiosis

Definition

Resulting Number

Genetically

Number of phases

List Phases

How are traits inherited?• Traits in DNA are passed from parent to

offspring• The offspring has a combination of traits

from both parents• Offspring traits can be predicted using

parent traits in a punnett square

What information do you need?• Each person’s genotype is written with

two letters• Uppercase = dominant

• if there is a dominant trait, it will always show!

• Lowercase = recessive • if there is a recessive trait, it will only show if

there is no dominant!• AA = Dominant aa = recessive• Aa = Dominant

How do you complete a punnett square?1. Add each parents genotype2. Carry letters across3. Carry letters down

AA

a

a

A A

a a

A

A

a

a

What does the punnett square tell you?• The boxes represent potential genotypes

of offspring if the two parents have offspring

• Can find ratios/percentages of the chance an offspring will have the dominant or recessive trait

Percent dominant trait?75%Ratio of dominant:recessive?3:1

Practice• Brown eyes are dominant to blue. The

father’s genotype is Bb. The mother has blue eyes.

1. Create a punnett square for the two parents.

2. What is the percent chance they will have a child with blue eyes?

3. What is the ratio of children with brown eyes versus blue eyes?