Chromosomes Flashcards
Chromosomal theory of inheritance
- Hereditary information is on GENES and genes are located on CHROMOSOMES
- Egg and sperm contribute equally to the genetics of offspring through their nuclei
Mitosis
Nuclear division that results in 2 daughter cells each containing identical numbers of chromosomes to the parent cell
Meiosis
Nuclear division that results in each egg and sperm containing half the number of chromosomes found in somatic cells
What is the determining factor of sex in drosophila?
The ratio of X chromosomes to autosomes
(1:1 ratio, female) (1:2 ratio, male)
Somatic cells
Diploid cells, most common cell in the body, contains two complete sets of chromosomes
Gametes
Egg and sperm, contain only one set of chromosomes, haploid cell
Nonhomologous chromosomes
- Contain different genes
- Do not pair at meiosis
Homologous chromosomes
- members of a chromosome pair
- contain the same genes, vary in alleles
- pair at meiosis
Sister chromatids
Identical alleles for all genes
Karyotype
An image of all the chromosomes of an individual, including size, number and shape
Early indications of chromosomes
Semen contains spermatozoa, frogs and sea urchins had the union of gametes, salamander cells had threadlike structures
Exceptions to XY chromosome determination
Reptiles: temperature dependent
Platapi: Females have 10X, males have XXXXXYYYYY
Clownfish: All males, fight to determine females
Heterogametic
Different chromosomes in each gamete (such as XY)
Homogametic
Same chromosomes in each gamete
What is the result of XX?
female in both drosophila and humans
What is the result of XY
male in both drosophila and humans
What is the result of XO
Male in drosophila, lethal (or Turner’s syndrome) in humans
What is the result of XXY
Female in drosophila, male with Klinefelter’s syndrome in humans
What is the result of XXX
Lethal in drosophila, female in humans
What is the result of OY
Lethal in both drosophila and humans
What is the result of XYY
Male in both humans and drosophila
