Genetics Vocab Notes

Genetics The study of heredity, how traits (characteristics) are passed down from one generation to the next Gene – sequence of DNA that codes for a protein & thus determines a trait

Chromosome Supercoils Coils Nucleosome Histones/proteins DNA double helix

Chromosomes Thread-like structures located inside the nucleus Each chromosome is made of protein and a single molecule of DNA. Passed from parents to offspring, DNA contains the specific instructions that make each type of living creature unique.

Karyotype A picture or display of all the pairs of chromosomes in numerical order based on size & shape

Homologous chromosomes Chromosomes that pair up and code for same genes, are the same size and shape. One from mother & one from father.

Autosomes Contain genes for all traits except for sex Chromosome pairs 1-22

Sex Chromosomes Chromosome pair #23 XX – 2X’s will make female XY – will make male

Traits A genetically determined characteristic or condition. Traits may be physical, such as hair color or leaf shape, or they may be behavioral, such as nesting in birds and burrowing in rodents.

Alleles Different forms of the same gene for a specific trait. Ex. Trait – eye color Alleles – blue, brown, green

Genotype The genetic makeup Refers to the alleles inherited for a particular gene Made up of 2 alleles

Phenotype Physical appearance of the alleles Ex. Blue eyes, tallness, being colorblind **Lots of misconceptions about dominant & recessive**

Phenotype

Talk to a Partner: Determine the genotype and phenotype of each flower

Recessive An allele expressed only when paired with another recessive allele. Written as a small letter. EX: b ~ blue eyes

Dominant An allele that is expressed when present Written as a capital letter EX: B ~ Brown eyes

Homozygous Having 2 identical alleles for a specific trait Purebred Can be dominant (BB) or recessive (bb)

Heterozygous Having 2 different alleles for a specific trait (Bb) Hybrid or carrier

Which gene is heterozygous?

Which gene is heterozygous?

Which gene is heterozygous?

Talk to a Partner: Determine which are Homozygous & Heterozygous

What would be the phenotypes of the 4 individuals below? R = Red r =white

Talk to a Partner: Use the following terms: Homologous chromosomes, genes, alleles, heterozygous, homozygous, dominant, recessive, genotype, phenotype

Which of these are genetically identical? A) Homologous chromosomes B) Sister Chromatids C) Neither

Which of these will pair up to form chromosomes during mitosis? A) Homologous chromosomes B) Sister chromatids C) Chromatids pair at random, so it’s impossible to predict

How would you answer?

An allele is: a) another word for a gene b) a homozygous genotype c) a heterozygous genotype d) one of several possible forms of a gene

Phenotype refers to the ______________ of an individual a) genetic makeup b) actual physical appearance c) recessive alleles

a) the dominant b) the recessive c) neither When the genotype consists of a dominant and a recessive allele, the phenotype will be like _________________ allele a) the dominant b) the recessive c) neither

Patterns of Gene Expression– 6 types 1. Dominant 2. Recessive

3. Codominance Two different alleles of the same trait are fully expressed Ex: Human blood types - A, B, AB, O Alleles: IA, IB, i IA & IB - codominant i - recessive (ii=type O blood)

Genotype IA IA or IAi IB IB or IBi IA IB ii Phenotype

IA IA or IAi A IB IB or IBi B IA IB A and B AB ii none O Genotypes Surface Proteins Phenotypes IA IA or IAi A IB IB or IBi B IA IB A and B AB ii none O

Examples

4. Incomplete Dominance Two different alleles of same trait combine (BLEND) to form a new expression of alleles Ex: Colors in flowers, red + whitepink

Comparison Codominance Incomplete dominance

5. Polygenic traits Trait produced from many alleles on more than one chromosome Ex. Hair color, skin color, eye color, height

6. Sex linked traits Traits carried on the sex chromosomes (mostly the x chromosome)

Ex. Colorblind, hemophilia Summary – 3-4 sentences