Define Sex chromosome
chromosome that directly controls the development of sexual characteristics
Define Diploid
cell that has two copies of each chromosome, one from an egg and one from a sperm
Define Haploid
cell that has only one copy of each chromosome
Define Meiosis
form of nuclear division that divides a diploid cell into haploid cells; important in forming gametes for sexual reproduction
Define Gametogenesis
process by which gametes are produced through the combination of meiosis and other maturational changes
Define Polar body
haploid cell produced during meiosis in the female of many species; these cells have little more than DNA and eventually disintegrate
Define Crossing over
exchange of chromosomes segments between homologous chromosomes during meiosis
Define Mutation
change in DNA sequence
Define Point mutation
mutation that involves a substitution of only one nucleotide
Define Frameshift mutation
mutation that involves the insertion or deletion of a nucleotide in the DNA sequence
Meiosis
sexual reproduction. Fusion of 2 gametes in a process that allows haploid cells to fuse called FERTILIZATION
Compare Mitosis and Meiosis
Mitosis
-Diploid cells (2)
-Occurs in the body cells
-2 genetically indexical cells
Meiosis
-Haploid cells that are (2n)
-Gametes formed in gonads
-Genetica variation occurs
Where does the sexual reproduction of meiosis occur?
in the sex organs (gonads) of animals. Production of gametes in animals- egg and sperm
Mitosis or Meiosis?
Cell division that produces 4, haploid cells. Reduction of chromosomes- half #.
meiosis
Genetic variation occurs ...
during meiosis
What happens during genetic variation?
random assortment of chromosomes during metaphase 1
When does crossing over occur?
prophase 1
How many pairs are there in a diploid organism?
23 (2 sets) chromosomes. Somatic cells. 46 chromosomes
How many pairs are there in a haploid organism?
1 set of chromosomes, held the number. Gametes, sex cells. 23 chromosomes
Homologous chromosomes- _____________ pair of inherited chromosomes (size. length, shape, and Loci)
matching
one from each parent. Each pair carries the same genre sequence of inherited characteristics
What do sex chromosomes determine?
the sex and characteristcs of an organism, 23rd pair. 2 sex chromosomes ( X and Y)
XX
female
XY
male
What is a karyotype?
digram showing a cell's chromosomes order from largest to smallest.
When and how do homologous chromosomes pair up?
karyotype includes pairing up of homologous chromosomes visually by size and shape and Loci (banding)
What are karyotypes used for?
to determine inherited genetic disorders (chromosome abnormalities) and sex
Genetic variations includes crossing over. Define crossing over and what it ensures
Exchanging of genetic material between homologous chromosomes ensures genetic diversity
______________ of organisms is influenced by crossing over. When does crossing over occur?
genetic diversity, prophase 1
What are the stages for meiosis (in order)
prophase 1
Prophase 1
-chromosomes pair to form tetrads (4 chromosomes)
-crossing over occurs
the cell is 2n (diploid)
-nuclear membrane disappears
Metaphase 1
-tetrads line up in the center of the cell
-cell is still 2n
Anaphase 1
-tetrads separate
-chromosomes separate independently
-cell is still 2n
Telophase 1
-nuclear membrane may or may not reappear
-daughter cells have formed
-cytokinesis occurred
-2 haploid (n) cells
Prophase 2
-DNA does not duplicate, nor crossing over
-nuclear membrane disappears
-cells are still n
Metaphase 2
-chromosomes line up in the middle of the cell
-cells are still n
Anaphase 2
-sister chromatids begin to separate
-cell still n
Telophase 2
-2 daughter cells have all separate
-4 new haploid cells, polar bodies
-cells are genetically different
What is a mutation?
Change in the DNA sequence
A mistake that is made during replication affects _______________
-Group of genes __________________, during meiosis
single gene, affects or entire chromosome
What are the causes for mutations?
-Errors in the DNA replication
-Crossing over of meiosis
Mutations can be...
-Harmful; diseases or deformities
-Helpful; organism is better able to survive
-Neutral; organism is unaffected
Define mutagens
It is chemical or physical event that cause mutations
Physical mutagens
high radiation, X-rays, high temperature, UV light
Chemical mutagens
asbestos, cigarette smoke
If mutations occur in germ cells...
gametes, that mutation is passed on the offspring;
If mutations occur in body cells...
mutation affects only the organism
Point mutation (substitution)
-one nucleotide is replaced with another nucleotide
-usually no change to protein occurs, Due to different combinations to make A.A
Ex. GAA to GAG� codes for the same protein
Insertions or deletions (frameshift)
-The adding or deleting of a nucleotide
-Causes a change in the remaining nucleotides likely altering the amino acid sequence (producing a nonfunctional protein)
Inversion
Nucleotide sequence that is reversed