Genetics Vocabulary

1
Genetics Vocabulary

• Mr. Singh
• March 2009

2
Trait

• Any physical feature that is passed down by genes
  from a parent to offspring
• Examples eye color, body hair, digestion enzymes
  (what you can eat), number of eyes, basic body
  structure

3
Gene

• A piece of genetic material that is able to code
  for a specific protein
• Genes code for the phenotype of a trait
• Blue eyes for eye color
• Body hair
• 32 teeth

4
Chromosome

• One copy of some of the genes that make-up the
  genotype of an organism
• Humans have 46 chromosomes

genes
5
Dominant/ Recessive Genes

• When someone has both a dominant and a recessive
  gene for the same trait, only the dominant gene
  will be used by the bodys cells
• Aa (A protein is made)
• AA (A protein is made)
• aa (a protein is made)

6
Genotype

• Describes the genes for a trait
• The genotype (genes) code for the protein that
  make the trait come out the way it does
  (phenotype).

7
Phenotype

• Phenotype describes the specific way a trait
  looks
• Trait eye color Phenotype brown eyes
• Trait bones Phenotype 206 bones

8
Meiosis

• The cell division that splits one cell into 4
  cells with ½ the number of genes as the original
  cell
• Normal cell 2 genes per trait
• Meiosis cell 1 gene per trait

9
Sex Cell

• The cell produced at the end of meiosis.
• The cells contain ½ the genes of the parents
• One gene per trait
• Humans egg and sperm

10
Fertilization

• When the male sex cell (sperm in humans) meets
  the female sex cell (egg is humans)
• This combines ½ the females genes with ½ the
  males genes to make one full cell.

11
Heterozygous

• Describes a genotype that has one dominant and
  one recessive gene for the same trait
• Aa Bb Ee
• Only used if one gene is dominant and one is
  recessive

12
Homozygous Dominant

• Describes a genotype that has two dominant genes
  for the same trait
• AA BB EE
• Only used if one gene is dominant and one is
  recessive

13
Homozygous Recessive

• Describes a genotype that has two recessive genes
  for the same trait
• aa bb ee
• Only used if one gene is dominant and one is
  recessive

14
Punnett Square

• A chart used to predict what offspring a set of
  parents MAY have
• It only shows you what is possible, not what WILL
  happen!

Aa x Aa
The parents should get ¼ children to be aa, but
they COULD get no aa offspring or all aa! THE
PUNNETT SQUARE IS ALL ABOUT PROBABILITY, NOT
DEFINITE ANSWERS!
15
Carrier

• Describes a person that carries or has the gene
  for a particular phenotype but does not show it
• Example B Brown b Blue
• Bb Shows brown but is carrier for the blue
  gene