Meiosis and DNA Replication and Heredity Characteristics

Crossing Over Definition

process that occurs during prophase 1 in which pieces of nonsister chromatids of homologous chromosomes are exchanged resulting in new genetic combination of chromosomes

Synapsis definition:

paring of homologous chromosomes in prophase 1 of meiosis

Chiasmata definition:

the site of crossing over of nonsister chromatids of homologous chromosomes

Homologous Chromosomes definition:

Chromosomes of the same shape size that contain genes for the same traits

Spermatogenesis definition:

Process of sperm production in males

Oogenesis definition:

Processes of egg production in females

What does sexual reproduction introduce in comparison to asexual reproduction?

Variability

What is variablity?

New genetic combinations/recombinant DNA

Things that add variation -

Crossing over

Independent Alignment of paired chromosomes when lining up at the equator during meiosis

Random fertilization

What does variation lead to?

Almost an unlimited amount of combinations

What can cause meiotic errors?

Nondisjunction

What is nondisjunction?

The failure of homologous chromosomes to separate in meiosis 1 or sister chromatids in meiosis 2

What does nondisjunction result in?

Aneuploidy

What is aneuploidy?

Condition in which one or more chromosomes or pieces of chromosomes are lacking or in excess

Example of aneuploidy -

giving rise to genetic abnormalities down syndrome/trisomy 21

Chapter 11 - DNA: The Molecule of Heredity Characteristics & Replication

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Definition for DNA Replication:

Process in which an identical copy of DNA is produced in a cell

What type of process is DNA replication?

A semiconservative process which means that at the end of DNA replication the new DNA will contain one original parent strand and a newly created daughter strand (that compliments the parent)

What does semiconservative mean?

Means using one old and new strand per replicated DNA

Primer Definition:

starter strand of DNA or RNA that is required for replication

What is primer in DNA replication?

In DNA replication it is a short strand of RNA

DNA Helicase definition:

enzyme responsible for unwinding and unzipping DNA during DNA replication

DNA Polymerase definition:

enzyme responsible for formation of DNA strand from a template

How does DNA polymerase work in regards to DNA replication?

includes adding nucleotide to growing 3’ end of strand of DNA

DNA Ligase definition:

Enzyme that unites Okazaki fragments of the lagging strand during DNA replication

Leading strand definition:

the daughter strand in DNA replication that is synthesized continuously

Lagging strand definition:

the daughter strand in DNA replication that is synthesized discontinuously

Steps of DNA replication:

• Helicase unwinds and unzips a double-stranded DNA molecule creating a replication bubble.

  • Each bubble contains two replication forks

• primer attaches the growing strand and is a starting point for nucleotide attachment

• DNA polymerase adds complementary DNA nucleotides to the 3’ growing end of the new daughter strand using a parent strand as a template

• DNA ligase joins Okazaki fragments of lagging strand as well as daughter strands to parent strands.

• Process results in two identical double-stranded DNA molecules

What did Erwin Chargaff do?

Establish Chargaff’s Rules in the late 1940’s

What is Chargaff’s Rules?

The number of purines in DNA always equals the number of pyrimidines, and that the amount of A equals T and G equals C.

What did Alfred Hershey and Martha Chase do?

In 1952, they used viruses to determine that DNA and non-protein were the genetic materials of living organisms.

What did Jams Watson and Francis Crick do?

Use Rosalind Franklin's X-ray diffraction photograph of DNA to build a model of DNA.

Determine that DNA was a twisted ladder with sugar and phosphate making up the sides of the ladder and the nitrogen bases making up the rungs with adenine and thymine and cytosine and guanine hydrogen bonds