DNA replication during the S phase of the cell cycle
What are Homologous Chromosomes?
Same genes in the same order but ofter not of the same forms (alleles) of those genes
What is Asexual reproduction?
Offspring derived from a single parent and are genetically identical to the parent
What is Sexual reproduction?
Two parents contribute genetic info. needed to reproduce offspring.
Off spring not genetically identical to either parent.
Greater chance for diversity
What is a Somatic cell?
Cells of the body
How do Somatic cells reproduce?
What are Germ Cells?
Cells present w/in the reproductive system
How do Germ cells reproduce?
Meiosis to produce gametes (egg and sperm)
What are Interphase cells?
The cell is not currently dividing
What is the Prophase of a cell?
Nuclear membrane breaks down, chromatin condenses to form chromosomes, spindle fibers begin to form
What is the Metaphase of a cell?
Chromosomes line up in single file on the equator. Homologous pairs do not associate.
What is the Anaphase of a cell?
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.
What is the Telophase of a cell?
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.
Where does Meiosis occur?
Only in the Germ cell
What is the result of Meiosis?
What happens during Prophase I of Meiosis?
Homologous chromosomes pair and crossing over occurs
What happens during Metaphase I of Meiosis?
Homologous chromosomes line up double file.
Their double file orientation is random (independent assortment)
What happens during Anaphase I?
Whole chromosomes pulled toward the poles. The genetic material moving toward each pole is different (because chromosomes of homologous pairs are not genetically identical)
What happens during Telophase I?
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.
What is the Interkinesis period?
The period between the division cycles
What is Prophase II of Meiosis?
Nuclear membrane breaks down, chromatin forms chromosomes.
(No crossing over since homologous pairs no longer present in the same cell)
What is Metaphase II of Meiosis?
Chromosomes line up on the equator single file
What is Anaphase II of Meiosis?
Chromatids pulled toward poles (as soon as they separate they are called chromosomes again)
What is Independent Assortment?
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
What is Nondisjunction?
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)
What causes Downs syndrome?
Three copies of chromosome 21
What is Aneuploidy?
Abnormal number of chromosomes.
What are some early genetic ideas?
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.
Who is a Rigorously trained Austrian monk who influenced early genetic ideas?
What are Alleles?
Alternate forms of the same gene (one copy on each homologous pairs)
What does Homozygous mean?
Alleles of the gene are the same on homologous pairs
What does Heterozygous mean?
Alleles of the same gene, different on homologous pairs.
What does Dominant mean (pertaining to genes)?
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
What does Recessive mean (pertaining to genes)?
Allele needs to be present in two copies to be expressed.
What is a Genotype?
Genetic make-up of an organism
What is a Phenotype?
Physical characteristics of an organism.
What is a Monohybrid cross?
Cross between two heterozygous individuals differing in a single trait
What is the Phenotypic ratio in f2 generation?
What is the Ratio of a dihybrid cross?
What are the Sex chromosomes?
X and Y
What does a gene being "sex" linked mean?
They are linked through the X chromosome
What is a Autosome?
All other chromosomes other then Sex chromosomes. Traits on these are referred to as being autosomal
What is incomplete dominance?
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
What is true about independent assortment according to Mendel?
Only holds true if two traits are on different chromosomes (as all of the traits studies by mandel happened to be)
What are linked traits?
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.
Which gender is most likely to have X-linked traits show?
Males because they only need to inherit one copy of the recessive allele to show the trait.
Who is Mendel?
An Atrian Monk with rigorous training in plant breeding, natural science and statistics
Reported his work in 1865
What is Mendel's Law of Segregation?
Alleles separate during the formation of gametes
What is the Punnet square?
The square we perform in class
l l l
l l l
l l l
l l l
l l l
l l l
What was Mendels Result Ratio average
What Autosomes skip generations?
Autosomal Recessive traits
Dominant traits do not skip generations
What is the product rule?
The chance that two independent events will both occurs equals the product of the chance that either event will occur alone
What is Polygenic inheritance?
Polygenic traits are those that are determined by multiple genes
Typically show a normal distribution w/in the population
What is the principle of Segregation?
Alleles go their separate ways during the formation of gametes
What can proven linked genes from being inherited together?
What is Ichthyosis?
Scaly brown skin
Lack of an enzyme that removes cholesterol from skin cells
Skin does peel off as it should
What is Hemophilia?
A blood clotting disorder
What is Duchenne Muscular Dystrophy?
Progressive muscle weakness
What is a Barr body?
An inactive X chromosomes in females
Even when there are more then 2
Which X is random
The result is a Genetic Mosaic
How are Mitochindria inherited
All are inherited from the mother.
What are some ways to obtain a sample of the fetus tissue for prenatal testing?
Withdraw from amniotic fluid
Chorionic villus sampling (CVS
Suction tube inserted through cervix, sample of Chorionic villus
What happens in the M stage of the Cell cycle?
The M cycle is when the cell is actually dividing (Mitosis)
What happens during the S stage of the cell cycle?
The S cycle is when the cell is replicating its DNA (Synthesis)
What happen during the G1 stage of the cell cycle?
The G1 cycle is A gap period after mitosis but before S phase
What happens during the G2 stage of the cell cycle?
G2 is a gap period after S but before Cell division
Getting ready to divide
What does apoptosis Mean
Cell self distraction
What is the Centromere?
The center of the chromosome that remains after replication.
What are Homologous chromosomes?
Same genes, same order but not always the same forms of those genes. Each derived from a different parent.
How many Homologous pairs of chromosomes do humans have?
23 Homologous pairs
What is Cytokinesis?
The division of the cytoplasm
Usually, but not always, follow mitosis
Microfilament shortening causes pinching in the cell membrane
Why do cells need to reproduce?
What is a zygote?
What the egg and sperm fuse a diploid cell
What is Crossing over?
When genetic information is exchanged between homologous chromosomes
What is Independent assortment?
When Homologous chromosome pairs line up double file during metaphase I of meiosis the order is random