Exam 3 Bio.txt

Cells divide by binary vision

This results in genetically identical cells

• Mitosis
• Interphase
• S
• G1 and G2

When cell is actually dividing

When cell is not dividing

• When DNA replicates
• DNA synthesis occurs

• Gap periods
• Contain a number of quality control checkpoints

Genetically identical arms of a chromosomes.

DNA replication during the S phase of the cell cycle

Same genes in the same order but ofter not of the same forms (alleles) of those genes

Offspring derived from a single parent and are genetically identical to the parent

• Two parents contribute genetic info. needed to reproduce offspring.
• Off spring not genetically identical to either parent.
• Greater chance for diversity

Cells of the body

By mitosis

Cells present w/in the reproductive system

Meiosis to produce gametes (egg and sperm)

The cell is not currently dividing

Nuclear membrane breaks down, chromatin condenses to form chromosomes, spindle fibers begin to form

Chromosomes line up in single file on the equator. Homologous pairs do not associate.

Spindle fibers shorten and draw chromatids (now called chromosomes) toward the poles. The genetic info heading toward each pole is identical because chromatids are genetically identical.

Chromosomes arrive at poles. Nuclear membrane reforms and chromosomes decondense to form chromatin. Cytokinesis or division of the cytoplasm usually takes place. Result is two genetically identical diploid cells.

Only in the Germ cell

Haploid gametes

Homologous chromosomes pair and crossing over occurs

• Homologous chromosomes line up double file.
• Their double file orientation is random (independent assortment)

Whole chromosomes pulled toward the poles. The genetic material moving toward each pole is different (because chromosomes of homologous pairs are not genetically identical)

Chromosomes reach poles. Nuclear membrane reforms. Cell divides in two. Each of these two cells will go through a second division cycle, which mechanistically is identical to mitosis.

The period between the division cycles

• Nuclear membrane breaks down, chromatin forms chromosomes.
• (No crossing over since homologous pairs no longer present in the same cell)

Chromosomes line up on the equator single file

Chromatids pulled toward poles (as soon as they separate they are called chromosomes again)

• During metaphase I of Meiosis, the way the homologous pairs line up is random - Thus the same parents can be produce genetically different gametes.
• This is why siblings of the same parent are different

Errors that occur during meiosis can cause an incorrect number of chromosomes to migrate toward the poles generating gametes (egg and sperm cells) with an abnormal number of Chromosomes (Aneuploidy)

Three copies of chromosome 21

Abnormal number of chromosomes.

• Pangenesis: Trait determining particles migrate to egg and sperm - determine the nature of the offspring. (Ancient greece)
• Blending (1800's) Offspring an intermediate blend of parents.

• G. Mendel
• mid 1800's

Alternate forms of the same gene (one copy on each homologous pairs)

Alleles of the gene are the same on homologous pairs

Alleles of the same gene, different on homologous pairs.

• Allele need only be present in one copy to be expressed
• Black is dominant to red
• If have on black and one Red gene the person will have black hair

Allele needs to be present in two copies to be expressed.

Genetic make-up of an organism

Physical characteristics of an organism.

Cross between two heterozygous individuals differing in a single trait

3:1

9:3:3:1

X and Y

They are linked through the X chromosome

All other chromosomes other then Sex chromosomes. Traits on these are referred to as being autosomal

• When both parents are dominant
• Such as the flower in class. dominant white, dominant red. when bred there offspring will be pink. When there off spring is bred 1/4 are red 1/2 are pink 1/4 are white. resulting in a 1:2:1 ratio

Only holds true if two traits are on different chromosomes (as all of the traits studies by mandel happened to be)

• Traits on the same chromosome
• More likely to be inherited together.
• Genes that are close together on the same chromosome will almost always be inherited together since there is little likelihood that a break will occur between them and they will be separated by crossing over
• The less often two genes on the same chromosome are inherited together the further apart they are on the chromosome (the > the crossover frequency, the further apart they are). this is used to map genes on chromosomes.

Males because they only need to inherit one copy of the recessive allele to show the trait.

• An Atrian Monk with rigorous training in plant breeding, natural science and statistics
• Reported his work in 1865

Alleles separate during the formation of gametes

• The square we perform in class
• ____________
• l l l
• l l l
• l l l
• --------------------
• l l l
• l l l
• l l l
• --------------------

3:1

• Autosomal Recessive traits
• Dominant traits do not skip generations

The chance that two independent events will both occurs equals the product of the chance that either event will occur alone

• Polygenic traits are those that are determined by multiple genes
• Typically show a normal distribution w/in the population
• Bell curve

Alleles go their separate ways during the formation of gametes

Crossing over

• Scaly brown skin
• Lack of an enzyme that removes cholesterol from skin cells
• Skin does peel off as it should

A blood clotting disorder

Progressive muscle weakness

• An inactive X chromosomes in females
• Even when there are more then 2
• Which X is random
• The result is a Genetic Mosaic

All are inherited from the mother.

• Amniocetesis
• Withdraw from amniotic fluid
• Chorionic villus sampling (CVS
• Suction tube inserted through cervix, sample of Chorionic villus

The M cycle is when the cell is actually dividing (Mitosis)

The S cycle is when the cell is replicating its DNA (Synthesis)

• The G1 cycle is A gap period after mitosis but before S phase
• Interphase

• G2 is a gap period after S but before Cell division
• Getting ready to divide

Cell self distraction

The center of the chromosome that remains after replication.

Same genes, same order but not always the same forms of those genes. Each derived from a different parent.

23 Homologous pairs

• The division of the cytoplasm
• Usually, but not always, follow mitosis
• Microfilament shortening causes pinching in the cell membrane

• Growth
• Replace
• Development
• Reproduce

What the egg and sperm fuse a diploid cell

When genetic information is exchanged between homologous chromosomes

When Homologous chromosome pairs line up double file during metaphase I of meiosis the order is random