End of Unit Review

E. Goodman

Covalent Bonds

These are the bonds that nucleotides are linked together by.

Head - 5’ end

This end is a phosphate group.

Tail - 3’ end

This end is a hydroxyl group (OH).

Antiparallel

Definition: running against each together.
The two strands of DNA molecules are ___.

Leading/Sense

One continuous piece of DNA (5’ to 3’).

Lagging/Anti-Sense

Made in discontinuous pieces called Okazaki Fragments (3’ to 5’).

Nitrogenous Bases

The two DNA strands are joined together by these bases.

Hydrogen Bonds

This kind of bond holds the bases together, allowing the formation of the double helix.

Adenine and Thymine

Complementary base pairing that form two hydrogen bonds.

Guanine and Cytosine

Complementary base pairing that form three hydrogen bonds.

Semi-Conservative

New copy that saves/conserves a portion of the original strand.

Helicase

First step - unwinds and unzips DNA double-helix.

RNA Primase

Second step - forms a segment known as the RNA primer.

DNA Polymerase

Third step - attaches nucleotides to DNA (5’ to 3’).

DNA Ligase

Fourth step - bonds the Okazaki Fragments into one continuous strand. Seals and completes the two copies that are duplicates of one another.

Step 1

• Helicase unzips and unwinds the DNA molecule by breaking the hydrogen bonds between the bases

  • Occurs in an area rich in A-T base pairs

Step 2

• The separated area of the DNA molecules is called a replication fork

  • Occurs at 100’s of places on a DNA molecules

  • Primase and binding proteins attach

Step 3a: Leading Strand

• DNA polymerase attaches to the 3’ end

• DNA polymerase builds the new strand in the 5’ to 3’ direction

  • This happens continuously

Step 3b: Lagging Strand

• RNA Primase attaches to the lagging strand adds RNA nucleotides (primer)

• DNA polymerase attaches to the primer and begins building the new strand in the 5’ to 3’ direction

  • This happens discontinuously produced Okazaki Fragments

Step 4

• RNA primers are removed and replaced by DNA nucleotides

  • Enzyme: Exonuclease

  • A second DNA polymerase proofreads the DNA sequence

Step 5

• DNA ligase seals up the gaps in the DNA backbone

Transcription

Definition: “writing/copying down into another form.”
First part in Protein Synthesis. mRNA creates codons from the genetic sequence of DNA.

Transcription Location

Occurs in the Nucleus.

mRNA

Made in the Nucleus. Translates Thymine to Uracil. “m” stands for “messenger.”

Translation

Definition: “change/convert from one form to another.”
Second part in Protein Synthesis. mRNA translates the codons into amino acids.

Translation Location

Occurs in the Ribosome.

rRNA + proteins

Create the Ribosome.

tRNA

• Stands for transfer

  • Transfers amino acids

  • Now have anticodons

Codons

A DNA or RNA sequence of three nucleotides that forms a unit of genomic information encoding a particular amino acid.

Anticodons

A sequence of three nucleotides in transfer RNA that binds to a corresponding codon and designates a specific amino acid.

Mutation

Definition: a change that occurs in our DNA sequences.

Mutation Causes

Mistakes are made when DNA is being copied through DNA replication. Results of exposure to environmental factors like UV light, cigarette smoke, and radiation.

Cell Repair

Cells can sometimes repair the error or possible damage before it becomes a fixed mutation (permanent).

Mutation Dis/Advantages

Advantages: Some can have a positive effect → genetic variation

Disadvantages: Some disrupt normal activity that can cause diseases like cancer. Environmental factors introduce radicals that attack DNA, causing these diseases.

Types of Mutations

Genes and Chromosomal Mutations

Point Mutation

Affect a single point in DNA, and one base is substituted for another.
Includes

• Missense

• Silent

• Nonsense

Missense

The substitution changes the amino acid. Essentially it changes it to not make sense. Creates an abnormal protein.
A type of point mutation.

Silent

The substitution does not change the amino acid. Change will occur, however, you won’t even know it’s there. Codons translate to the same product.

Nonsense

The amino acid is changed to a “stop” codon. “Does not make sense to stop the code right in the middle.” A lot of the times when the protein isn’t made.

Frameshift Mutations

The “reading frame” changes, which changes the amino acid sequence.
Includes:

• Deletion

• Insertion

Creates a domino effect, possibly producing a malfunctioning protein.

Deletion

A base is lost (-).

Insertion

An extra base is added (+).

Another Term for Sperm and Egg

Gametes/Sex Cells

Human Diploid Number

46 autosome chromosomes

Human Haploid Number

23 allosome chromosomes

Product of Meiosis

4 genetically different gametes

Zygote

Fertilized egg

Hybrid

Offspring of crosses between parents with pure, different traits.

Haploid

Contains a single set of chromosomes (n). Formed by the process of meiosis.

Diploid

Contains two sets of chromosomes (2n).

Somatic

Body cells

Oswald Avery

Confirmed that DNA is the carrier of heritable information.

Rosalind Franklin

Used X-ray crystallography to capture a rough image of the DNA double helix.

Watson and Crick

Won the Nobel prize for determining the structure of DNA.

Nucelotide Monomer

Consists of Phosphate, Deoxyribose and a Pyrimidine (1 ring) or Purine (2 rings) base.

DNA

Abbreviation for deoxyribonucleic acid. A “recipe” for every living organism. Carries instructions packaged in segments called genes. Has sections that code for protein.

Genes

A set of specific instructions that can be switched on or off depending on what is needed in a specific cell. There are many located in the DNA.

DNA Analogy

“It’s like a cookbook which contains a variety of recipes with different instructions and ingredients.”

DNA Functions

Gives instructions to the amino acids to construct into the perfect protein shape.

Protein Construction Cycle

DNA creates RNA, RNA creates Protein, which form life.

Base Pairing Rule

% of Adenine = % of Thymine
% of Cytosine = % of Guanine

Adenine Base Pairing

Adenine bonds with Thymine [A - T].

Cytosine Base Pairing

Cytosine bonds with Guanine [C - G].

Uracil Base Pairing

Adenine bonds with Uracil (RNA only) [A - U].

Erwin Chargaff

Name of the man who created base pairing rules for DNA.

Parts of a Nucleotide Molecule

Sugar (Deoxyribose), Phosphate and Nitrogen.

Backbone of DNA

Alternating groups of Deoxyribose (sugar) and Phosphate.

Purines

Contain two rings, overall larger than pyrimidines. Adenine and Guanine are this type.

Pyrimidines

Contain one ring, overall smaller than purines. Cytosine, Thymine and Uracil are this type.

Nitrogenous Bases

Adenine, guanine, cytosine and thymine are used as this kind of base in nucleotides.

Nucleotides

Subunits that make up DNA.

Deoxyribose

A five-carbon sugar.

Hydrogen Bond

A type of bond that holds the double helix of DNA together. These bonds are weak, however there is no damage to the nitrogenous bases if damaged/broken.

Double Helix

Two strands of nucleotides twisted around each other.

Meiosis Definition

The creation of gametes for sexual reproduction. This process is different from mitosis.

Interphase

Before meiosis occurs, all of the DNA inside the nucleus of the parent cell is replicated.

Chromatin

Uncoiled stringy DNA.

Human DNA Distribution

Half of your DNA comes from your mother and half from your father.

Alleles

Different forms of a gene.

DNA Synthesis

When DNA copies itself during interphase.

Meiosis I

Separated into 5 phases:

1. Prophase I

2. Metaphase I

3. Anaphase I

4. Telophase I

5. Cytokenesis I

Prophase I

Start/beginning of Meiosis. The two chromosomes may exchange fragments by a process called crossing over.

• Nuclear membranes disintegrate so the spindle fibers have access to the chromosomes

Metaphase I

Middle - Proper Division.

1. Chromosomes line up in the middle of the cell

2. Spindle fibers attach to the centromere of the chromosomes

   • Lining is important because you need to get equal numbers of chromosomes

Anaphase

Apart and away.

• Chromosomes are pulled apart and away from each other

  • “Reeling in”

• Two copies to one (sister chromatid)

Telophase

“Two.”

• Now have two separate piles of chromosomes - two distinct nuclei form

• Spindle fibers disappear

Cytokinesis

“Cut/Cleave”

• The cell now cuts into two separate cells

• Cytoplasm and organelles are now equally divided

Chromosomal Mutations

These disorders occur when there are alterations to structure or changes in the overall number of chromosomes.

Karyotypes

Visual organizations for chromosome pairing and existing mutations/disorders that are present.

Karyotype Slots

Slot 1 is the largest, all the way down to slot 22, the smallest. These are called autosomes.

Chromosomal Banding

Based on this, it shows where there are active genes.

Allosomes

Sex chromosomes, listed as:

• XX - Female

• XY - Male

Notations

Amount of chromosomes and type of sex.
Examples:

• 46, XY

• 46, XX

Breakage

Breakage of a chromosome can lead to four types of changes in chromosome structure:

• Deletion

• Duplication

• Inversion

• Translocation

Deletion

Removes a chromosomal segment. A type of chromosomal breakage.

Duplication

Repeats a segment. Changes the size of the chromosome. A type of chromosomal breakage.

Inversion

Reverses orientation of a segment within a chromosome. Flips, no change in size. A type of chromosomal breakage.
Definition: opposite

Translocation

Moves a segment from one chromosome to another. A type of chromosomal breakage.

Anaphase I & II - What things separate?

Anaphase I: homologous chromosome pairs
Anaphase II: sister chromatids

Most mutations commonly occur in these phases.

Nondisjunction

Either homologous chromosomes or chromatids do not separate normally in the process of Meiosis.

Aneuploidy

Results from the fertilization of gametes in which nondisjunction meiosis errors occurred. One or a couple of chromosomes missing or present in surplus.
Offspring with this condition have an abnormal number of chromosomes.