Meiosis and Mendel's Genetics (LHS SS W4)

gene

A segment of DNA on a chromosome that codes for a specific trait.

genetics

The study of heredity and the variation of inherited characteristics.

Gregor Mendel

The father of genetics that first worked with different characteristics of pea plants.

punnett square

A diagram used to predict the probability of how traits could be passed from parent to offspring.

DNA

Chemical molecule containing the genetic information that makes up the chromosomes.

alleles

Alternative forms of a gene.

homozygous

Two of the same alleles, for example PP, aa or TT.

heterozygous

Two different alleles, for example Tt or Bb.

dominant

More common traits that mask or cover the other versions of those traits.

recessive

The LESS common trait in which the allele is only expressed when two copies are present.

homologous

A matching set of chromosomes that have the same genes, one copy from each parent.

phenotype

An organism's physical appearance based on DNA inherited from parents.

genotype

An organism's genetic makeup, or combination of alleles inherited from parents.

nucleus

Control center of the cell containing DNA.

asexual reproduction

Involves only one parent and produces offspring that are identical to the parent.

sexual reproduction

Reproduction that requires two reproductive gametes where offspring are a combination of the two parents.

heredity

The passing of traits from parent to offspring.

Law of Segregation

Mendel's idea that during meiosis the two copies of chromosome pairs separate so that only one is passed on.

Law of Independent Assortment

Mendel's idea that traits are inherited separately and one trait does not control another.

crossing over

Process during prophase I or metaphase I of meiosis when parts of homologous chromosomes are broken off and exchanged.

meiosis

Cell division which produces haploid gametes.

gametes

Reproductive cells such as egg or sperm cells.

somatic cells

Body cells, such as skin, bone or nerve cells.

haploid

A cell containing one chromosome from each homologous pair, in human only 23 chromosomes.

diploid

Any cell containing a full set of chromosomes, where they are found in homologous pairs.

spindle fibers

Structures responsible for moving chromosomes to opposite ends of the cell during anaphase.

centromere

Connection between sister chromatids that breaks when those separate during anaphase II of meiosis.

linked

Genes located near each other on a chromosome that are commonly inherited together.

karyotype

A picture of human chromosomes, showing all 23 homologous pairs.