Everything Genetics!

What is the cell cycle?

Sequence of events that includes growth, DNA synthesis, and cell division.

What are the two phases of the Cell Cycle?

Interphase and the Mitotic Phase

What is Interphase?

Phase in which cells grow, DNA is replicated, and cell performs normal metabolic processes in preparation for division

How many and what are the subphases are in Interphase?

3. G1, Synthesis, and G2.

What is G1?

A subphase of Interphase

The cell grows, proteins are made, and routine metabolic processes are performed

What is Synthesis?

A subphase of Interphase

DNA is replicated

What is G2?

A subphase of Interphase

Final preparations are made to divide and organelles are copied

What stage of the cell cycle do Eukaryotic cells spend most of their time in?

Interphase

What are regulatory proteins?

Proteins that control the cell cycle at specific checkpoints

How many checkpoints are their in the cell cycle?

3

When and what occurs at the Cell Growth Checkpoint?

Occurs in the middle of G1

Regulatory proteins decide if the cell is eligible to move forward in the cycle.

When and What occurs at the S Checkpoint?

Occurs in the middle of S phase

Regulatory proteins check to see if the DNA was replicated properly

Why are the daughter cells created from Mitosis genetically identical?

Because of DNA replication in the S phase

Where does DNA replication occur?

The nucleus

What type of proteins makes DNA replication happen?

Enzymes

What does Helicase do in regards to DNA replication?

An enzyme that unwinds the 2 stranded DNA and breaks the hydrogen bonds between nitrogenous bases

What structure is formed during DNA replication?

A DNA replication fork

What does DNA polymerase do in regards to DNA replication?

An enzyme that goes along the DNA strands and builds a complementary strand to the exposed base pairs of the parent DNA

What does Primase do in regards to DNA replication?

an enzyme that builds a short RNA primer on the lagging strand of DNA

What happens when the DNA Replication Fork is created?

A leading and lagging strand of DNA is established with the lagging strand being on top and the leading stand being on the bottom.

What is the lagging strand of DNA?

The DNA strand that is above the leading strand which is put together using a primase and okazaki fragments.

3’ to 5’ direction

What is the leading strand of DNA?

The DNA strand that DNA polymerase constructs in the 5’ to 3’ direction

What is DNA Replication?

The process in which a cell’s entire DNA is copied

What are Okazaki Fragments?

short fragments of DNA that comprise the lagging strand of DNA

What does 3’ to 5’ and 5’ to 3’ have to do with DNA replication?

Each DNA strand (the lagging and leading strands) have a direction.

A 5’ end has a terminal phosphate group.

A 3’ end has a -OH group.

What is a summary of DNA Replication?

DNA helicase unwinds the DNA. Proteins hold the two DNA strands apart while DNA polymerase creates a complementary DNA strand to the leading strand. Primase and Okazaki fragments work together to create complementary DNA strands to the lagging strand. Replication continues until new DNA has been made consisting of old/original DNA and new DNA.

All cells in an organism (except gametes)…

have the same DNA

What is Fertilization?

When egg and sperm (in humans) meets

What is the result of Fertilization?

A Zygote

When do Stem cells begin being made?

After the cells in a Zygote divide 4-8 times

What type of stem cells are made after 4-8 divides in a Zygote?

Embryotic Stem Cells

What are Embryotic Stem Cells?

A type of stem cell which can make all kinds of cells

Are referred to as totipotent

What does totipotent mean?

means they can make all types of cells

What are pluripotent stem cells?

A type of cell that can make one of the three primary groups of cells

What are the three types of pluripotent stem cells?

Ectoderm, Mesoderm, and Endoderm

What are multipotent stem cells?

A type of stem cell that can only make a certain type of cell

Example. Muscle Stem Cell or Skin Precursor Cell

What are unipotent stem cells?

A type of stem cell that can only make more of itselfs (can’t differentiate)

Example. Cheek Cell or Red Blood Cell

What is the scale for Stem Cell Differentiation?

Embryonic Stem Cell (totipotent) → pluripotent →multipotent→unipotent

What is cell differentiation?

The process by which stem cells produce specialized cells

What occurs to make cell differentiate?

Segments of genetic material is activated or repressed making cells more and more differentiated

What are homologous chromosomes?

Similar chromosomes with the same genes but different alleles

What are alleles?

Are alternate forms of genes found on chromosomes

What does the sequence of your DNA determine?

Determines how proteins are made and what your traits are (physically)

What are diploid cells?

Cells that have two sets of chromosomes equalling 46 total

What are haploid cells?

Cells that only have one set of chromosomes equalling 23 total

What type of cell are the majority of your body cells?

Diploid

What type of cell are gametes?

Haploid

What is Meiosis?

A type of cell division which produces gametes

How many rounds are in Meiosis?

2

What is the result of meiosis?

4 haploid cells which means each cell has 23 chromosomes, not pairs

Why are homologous chromosomes not identical?

Because of different alleles

What happens prior to meiosis?

DNA replicates

What occurs in Prophase 1?

Chromosomes line up together, crossing over may occur, chromosomes condense, and spindles form

What is crossing over?

A process which exchanges DNA between chromosomes resulting in a new combination of alleles

What occurs in Metaphase I?

Chromosomes line up at the equator of the cell and spindle fibers attach to the centromere of the chromosomes at random

What occurs in Anaphase I?

Chromosomes are pulled to each pole of the cell by the shortening of spindle fibers

What occurs in Telophase I?

The spindle fibers dissolve and the nuclear membrane does not reform.

What occurs after Telophase I?

Cytokinesis occurs almost instantly

What occurs in Prophase II?

Chromosomes recondense

What occurs in Metaphase II?

Chromosomes line up at the equator of the cell and spindle fibers attach to the centromere

What occurs in Anaphase II?

Sister chromatids separate as the spindle fibers shorten

What occurs in Telophase II?

Nuclear membrane begins forming around the around the newly separated chromosomes

What occurs right after Telophase II?

Cytokinesis occurs creating four gametes that are genetically different

What is gel electrophoresis?

a laboratory method that is used to separate DNA, RNA, and proteins according to molecular size

What does electrophoresis mean?

the movement of charged particles through the gel through a electric field

What types of charges are used during gel electrophoresis and what are their purpose?

A positive and negative charge is used.

The negative charged is used to repel the DNA molecules because DNA is also negatively charged.

The positive charge is placed at the end of the gel so the DNA moves towards it.

What is a mutation?

A change in nitrogenous bases of DNA or RNA

What is a Mutagen?

Something that causes a mutation

What is a Germline Mutation?

A mutation in a gamete and can be passed to offspring

What is a Somatic Mutation?

A mutation that occurs in a somatic (non-gamete) cell

Not serious and only occurs in one cell or daughter cells Cannot be passed onto offspring

What is Chromosomal Alteration?

A mutation that changes chromosome structure/genetic material

Occurs when part of a chromosome breaks off and doesn't rejoin correctly

Can occur because of deletion, duplication, inversion, insertion, or translocation

What is a Point Mutation?

A mutation that changes one nucleotide

Less serious

Several Types

What is a Frameshift Mutation?

A mutation in which a nucleotide is deleted or inserted causing everything to shift over, greatly impacting protein synthesis

What is a Genetic Disorder?

A disease caused by a gene mutation

What causes a mutation?

Most are accidental and random but some can be caused by mutagens.

What are some examples of a mutagen?

Chemicals (Cigarette smoke, Barbecuing)
Infectious Agents (HIV)
Radiation (UV radiation, X-Rays)

How many different types of point mutations are their and what are they?

3. Silent Mutation, Missense, and Nonsense

What is a Silent Mutation?

A type of point mutation, in which a mutated codon (a nitrogenous base gets changed) codes for the same amino acid

What is a Missense Mutation?

A type of point mutation, in which a mutated codon (a nitrogenous base gets changed) codes for a different amino acid

What is a Nonsense Mutation?

A type of point mutation, in which a mutated codon (a nitrogenous base gets changed) codes for a stop codon, ending the protein synthesis early

What is nondisjunction?

A type of chromosomal alteration that occurs when chromosomes or sister chromatids do not separate equally in anaphase I or anaphase II.

What are so examples of nondisjunction?

Trisomy 21 (having an extra 21 chromosome: causes down syndrome)

Trisomy 18 (having an extra 18 chromosome: causes edwards syndrome)

Klinefelter’s Syndrome (a male having two X chromosomes)

Turners Syndrome ( a female with one X chromosome)

What occurs during gel electrophoresis?

A negative current of electricity is used to move DNA through a semipermeable gel towards a positive current, resulting in DNA being sorted by size.

What are the 5 steps in gel electrophoresis?

1. Make the gel
2. Set up the gel apparatus
3. Load the DNA sample into the gel
4. Hook up the electrical currents and “run” the gel
5. Stain the gel and analyze the results

When the results of gel electrophoresis are printed on paper, there are dark bands present to indicate the results. What do these dark bands represent?

They represent the different molecular sizes of the DNA fragments tested

What are the centrioles?

An organelle that is only present during cell division, that spindle fibers are attached too

Also called a spindle apparatus

What charge is placed on the top of the gel apparatus?

A negative charge

What charge is placed on the bottom of the gel apparatus?

A positive charge