Unit 8: Meiosis and Genetics Flashcards
meiosis
the process by which sex cells divide to create eggs and sperm
fertilization
when a sperm and egg combine
gametes
sex cells, eggs and sperm, the cells after meiosis II
ovaries and eggs
female reproductive organs and gametes, eggs come from ovaries
testes and sperm
male reproductive organs and gametes, sperm come from testes
zygote
a fertilized egg, the earliest stage of development of a new organism
embryo
a new organism in development
homologous chromosomes
chromosomes that carry the same genes (even if different alleles), pair up and divide in meiosis I
autosomes
normal chromosomes (non-sex chromosomes)
sex chromosomes
chromosomes that are linked to an individuals biological sex, X or Y, females typically have XX and males typically have XY
haploid
cells that only have half of their original genes, all cells produced by meiosis (when done correctly) are haploid, written as N
diploid
cells that have their original number of chromosomes, all cells produced by mitosis are diploid, as well as cells that go into meiosis, written as 2N
crossing-over
In prophase I, chromosomes cross over each other and exchange some of their genes
karyotype
A visual representation of an individual’s chromosomes
nondisjunction
when an error occurs in meiosis so that chromosome do not split properly
polar body
the smaller of 2 cells produced at the end of meiosis II in females, polar body degenerates, the other cell is larger and can go on to be fertilized
x-inactivation
in people with two x chromosomes, one of them becomes inactivated so two of the same chromosome are not trying to “work” at the same time
Barr body
the inactivated x chromosome condenses into a Barr body which is stored inside the cell
trait
a characteristic of an individual, such as eye color (eyes can be blue, brown, green, etc.)
gene
a part of a chromosome that codes for trait (ex: eye color)
alleles
the variant of a gene that codes for the same trait but different characteristic (ex: blue eyes)
genotype
the genes an individual has
phenotype
the physical characteristics an individual has (based on their genotype)
homozygous
having 2 of the same allele (either 2 dominant or 2 recessive)
heterozygous
having 2 different alleles (one dominant and one recessive)
monohybrid
a cross of individuals that vary on one trait
dihybrid
a cross of individuals that vary in two traits
Gregor Mendel
The scientist who discovered the basic principles of inheritance through his work breeding pea plants
law of segregation
alleles separate randomly into gametes
law of independent assortment
allows for 4 possible gametes with combinations of traits that are different from the parents
pedigree chart
a diagram that represents the inheritance of certain traits or genes through families over generations
punnett square
diagrams used to find the probabilities that offspring will have certain genotypes (which can determine phenotype)
recessive
to express a recessive trait, an individual needs both recessive alleles
dominant
to expressive a dominant trait, an individual only needs one dominant allele (can have 2)
carrier
a female who has the gene for a certain condition hidden in a recessive gene (because women have 2 X chromosomes, a heterozygous female would not express it)
purebred (true-breeding)
an individual with two identical alleles, homozygous
incomplete dominance
when one trait does not completely hide the other trait, a blended phenotype is expressed
codominance
there is more than 1 dominant allele, a heterozygous individual expresses both (think different color spots on fur)
sex-linked
traits that are determined by genes found on sex chromosomes (X or Y), usually the X chromosome
polyallelic (multiple alleles)
occurs when a gene has more than two versions, leading to multiple phenotypes (think human blood type)
polygenic
traits that are determined by a combination of genes
