Regents Biology 22 pairs of autosomes Common to both male and female 1 pair of sex chromosomes Classes of chromosomes

Regents Biology Genetics Why do we look the way we do? How were these brown eyes made?

Regents Biology  Genes  Sections of DNA that contains instructions for making proteins  Control the TRAITS of the individual

Regents Biology Inheritance of genes  On the chromosomes passed from Mom & Dad to offspring are genes  may be same information  may be different information eye color (blue or brown?) eye color (blue or brown?)

Regents Biology Inheritance of genes  Genes come in “versions”  brown vs. blue eye color  alleles  Alleles are inherited separately from each parent  brown & blue eye colors are separate & do not blend  either have brown or blue eyes, not a blend

Regents Biology How does this work? eye color (brown?) hair color eye color (blue?)  Paired chromosomes have same kind of genes  but may be different alleles

Regents Biology Traits are inherited as separate units 1 from Mom 1 from Dad  For each trait, an organism inherits 2 copies of a gene, 1 from each parent  a diploid organism inherits 1 set of chromosomes from each parent  diploid = 2 sets of chromosomes homologous chromosomes

Regents Biology Will you have blue or brown eyes? eye color (B = Brown) eye color (b = blue)  Dominant traits (upper case)  Hides recessive alleles  Can be expressed if you inherited 1 dominant allele or both dominant alleles  Recessive alleles (lower case)  Hidden by dominant alleles  The recessive trait will only be expressed if you inherited both recessive alleles  brown is dominant over blue  blue is recessive to brown

Regents Biology How do we say it? BB= brown eyes bb= blues eyes Bb= brown eyes 2 of the same alleles Homozygous 2 different alleles Heterozygous homozygous dominant homozygous recessive

Regents Biology Genetics vs. appearance  There can be a difference between how an organism looks & its genetics  appearance or trait = phenotype  brown eyes vs. blue eyes  genetic makeup = genotype  BB, Bb, bb 2 people can have the same appearance but have different genetics: BB vs Bb

Regents Biology Making gametes BB= brown eyes bb= blues eyes Bb= brown eyes BBbbBbBb Remember, only one version for each gene goes into each gamete Remember meiosis!

Regents Biology Punnett squares: A way to predict possible offspring Bb x Bb possible male sperm Possible female eggs X BB BbBbbb BbBb B b Bb

Regents Biology  In humans & other mammals, there are 2 sex chromosomes: X & Y  2 X chromosomes  develop as a female: XX  an X & Y chromosome  develop as a male: XY Genetics of Sex XY X X XX XY 50% female : 50% male XX

Regents Biology IN PEA PLANTS Tall is dominant over short TALL = ____ SHORT = ____ LET’S MAKE A CROSS! TALL SHORT X What do you need to know before you begin?

Regents Biology TALL parent What are the parent alleles? T T Genotype:____________   What gametes can it make?

Regents Biology SHORT parent What are the parent alleles? t t Genotype:____________   What gametes can it make?

Regents Biology GENOTYPE _____ PHENOTYPE _______ _____% of the offspring or ___/4 will be…

Regents Biology Genetics vs. appearance  There can be a difference between how an organism looks & its genetics  appearance or trait = phenotype  brown eyes vs. blue eyes  genetic makeup = genotype  BB, Bb, bb 2 people can have the same appearance but have different genetics: BB vs Bb

Regents Biology Co-dominance  2 alleles affect the phenotype equally & separately  not blended phenotype  human ABO blood groups  3 alleles  I A, I B, i  I A & I B alleles are co-dominant  glycoprotein antigens on RBC  I A I B = both antigens are produced  i allele recessive to both

Regents Biology Codominance

Regents Biology Environmental effects  Phenotype is controlled by both environment & genes Color of Hydrangea flowers is influenced by soil pH Human skin color is influenced by both genetics & environmental conditions Coat color in arctic fox influenced by heat sensitive alleles