Genetics Review

Deoxyribonucleic Acid

DNA is the building block of life.

ALL living things have DNA.

DNA is double stranded

DNA is made up of NUCLEOTIDES

DNA makes RNA, which makes PROTEIN

Monomers (building blocks) of DNA

3 parts

Ribose Sugar

Phosphate Group

Nitrogenous Base (this is the most important part - A, T, C, G)

A nucleotide contains one nitrogenous base and they pair together.

A - T (Adenine - Thymine)

C - G (Cytosine - Guanine)

DNA is arranged into chromosomes.

Humans have 46 chromosomes.

You get 23 chromosomes from each parent.

Genes are sections of DNA that code for a protein.

There are multiple genes on each chromosome.

Each pair of chromosomes you get from each parent have the SAME genes, but might be a different version of the gene.

An allele is a version of a gene. You can get different alleles from your parents.

The gene might be for Hair Color.

You might get the allele for brown hair from one parent and the allele for black hair from the other.

Some alleles are stronger than others, and you will always see that version of the gene.

Dominant (stronger) - uppercase letter

Recessive (weaker) - lowercase letter

The genotype is the combination of the alleles you get from both parents.

Uppercase letters are DOMINANT.

Lowercase letters are RECESSIVE.

There are always 3 possible combinations - AA, Aa, aa

Phenotypes are what you see.

The gene is for eye color.

The phenotype is the actual color of the eye (Brown, Blue, Green)

Purple flowers are dominant.

White flowers are recessive.

Purple is stronger than white so the flower will be purple if it has at least 1 purple allele.

Purple Genotype: PP or Pp

White Genotypes: pp

Homo = same (AA or aa)

Hetero - different (Aa)

Homozygous means that both parents gave you the same allele.

Heterozygous means the parents gave different alleles.

​Write a paragraph explaining how a heterozygous parent can pass on either the dominant or the recessive trait. Give examples.