Genetics - Exam 3

2 mechanisms of inheritance

1. DNA replication

2. Cell Division

2 types of cell division

1. Mitosis

2. Meiosis

What is reproduction?

To produce more individual cells or organisms

What is sex?

To produce new combo of alleles, recombination, allowing for genetic diversity

Examples of asexual reproduction

Binary fission in bacteria

Mitosis in eukaryotic organisms

Examples of sexual reproduction

Meiosis and union of gametes (sperm and ova)

In order for a population to adapt to a new environment, _______ in our traits must be present

Variation

What are the 2 origins of genetic diversity?

1. Mutation

2. Sex

What are the basics of DNA replication?

• Each strand serves as a template

• Base pairing rules allow replication

What is the team of DNA replication?

• Helicase

• Topoisomerase

• SSB’s

• DNA polymerase

• Primase

The function of helicase is to…

Unwinds DNA

The function of topoisomerase is to…

Release mechanical stress of unwinding

The function of SSB’s are to…

Keep DNA single stranded

What does SSB stand for?

Single-stranded binding proteins

The function of DNA polymerase is to…

Add base pairs to template strand

What are the 2 restrictions of DNA polymerase?

1. Only can occur in 5’to 3’ direction

2. Primer is needed to begin synthesis

The function of a primase is to…

Make primers made of RNA

DNA replication is semi-__________ (daughter strand)

Conservative

What does it mean when we say DNA replication is semi-conservative?

Daughter molecules are half old, half new

Daughter molecules are half old, half new. This means…

One strand is used as a template to make a new one, which is then retained in the daughter molecule 

DNA replication is semi-________ (5’ to 3’)

Discontinuous

DNA replication is semi-discontinuous, meaning that…

one strand is made continuously while the other is made in short, discontinuous fragments.

Leading strand is made…

continuously in the same direction as the replication fork moves.

Lagging strand is made…

discontinuously in short fragments (called Okazaki fragments) in the opposite direction of the fork movement.

Short fragments of the lagging strand are called ________ ________

Okazaki fragments

DNA ligase is an enzyme, which function is to…

Link DNA by phosphodiester bonds

DNA replication is bi-_______

Directional

DNA replication is bi-directional, meaning…

It proceeds outward from the origin in 2 opposite directions

Replication forks

Regions that form when the double-helix unwinds during replication

The problem with linear DNA is…

Incomplete replication of telomeres

What solves the problem with linear DNA?

Telomerase

Telomeres get shorter and shorter with each _________

replication

Telomerase function is to…

facilitate replication of telomeres

Telomerase are turned ____ in most body cells

Off

Telomerase are turned ___ in gamete producing cells

On

What is happening during interphase?

• Cell not dividing

• Working its ass off

3 stages of interphase

1. G1

2. S

3. G2

What happens during G1 of Interphase?

Cell growth

What happens during S of interphase?

Replication

What happens during G2 of interphase?

Further prep for cell division

2 types of cell division

Mitosis and Meiosis

What is the goal of mitosis?

Produce 2 genetically identical daughter cells from one parent

What is the role of mitosis in unicellular organisms?

Asexual reproduction

What is the role of mitosis in multicellular organisms?

(HINT: 3 R’s)

Repair, regeneration, reproduction?

______ and ______ cells can undergo mitosis

Haploid and Diploid

Steps of mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

What occurs during prophase?

Condensing of chromosomes

What occurs during Metaphase?

Chromosomes line up

What occurs during anaphase?

Sister chromatids separate

What occurs during Telophase?

New nuclei form

_____ ______ hold sister chromatids from centromeres

Spindle fibers

Between Interphase and Prophase, what occurs?

Condensation

Between Anaphase and Telophase, what happens?

Cell divides

Meiosis is…

Separation of homologous chromosomes and sister chromatids

What is the main goal of meiosis?

Create genetic diversity

Only _____ cells can undergo meiosis

Diploid (or higher ploidy)

There must be at least _ sets of chromosomes for meiosis to occur

2

What occurs during meiosis 1?

Homologous pairs separate

Tetrads align

Tetrads are…

pairs of homologous chromosomes

What occurs during prophase 1?

1. Synaptonemal complexes form tetrads

2. Crossing over occurs

3. Condensation occurs

4. Chiasmata can be seen

What is a chiasmata?

Visual evidence that crossing over has occurred

What happens during metaphase 1?

Tetrads align

What happens during anaphase 1?

homologous pairs separate

Equal segregation

Independent assortment

What is equal segregation?

homologous chromosomes separate and move to opposite poles.
Each daughter cell gets one chromosome from each pair, keeping the genetic material balanced.

What is Independent assortment?

Random alignment and separation of genes on different chromosomes

In meiosis 1, how are resulting cells different from original cell?

• ½ the number or chromosome sets

• ½ the amount of DNA

In meiosis 2, how are resulting cells different from original cell?

• Same number or chromosome sets

• ½ the amount of DNA

What is Crossing over?

homologous chromosomes exchange DNA segments at chiasmata.

Each gamete will be unique because of ______ _______ and ______ _______

Independent assortment and Crossing over

Meiosis produces…

Gametes and spores

Gametic meiosis is a ________ dominant life cycle

diploid

Who uses gametic meiosis?

Animals and some protists

Zygotic meiosis is a _____ dominant life cycle

haploid

What uses zygotic meiosis?

Fungi and some protists

Sporic meiosis is _________ __ _______ life cycle

Alternation of generations

What uses sporic meiosis?

Plants

Results of equal segregation are ___ between sexes

Same

Agouti fur

Strand of hair containing multiple colors

The likelihood of 2 or more events is found by _______ the probabilities

Multiplying

The likelihood of 1 our of 2 or more events is found by _______ the probabilities

Adding