Regents Biology

22 pairs of autosomesCommon to both male and female

1 pair of sexchromosomes

Classes of chromosomes

Regents Biology

Genetics

Why do we look the way we do?

How were these brown eyes made?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

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 eyesbb = blues eyes

Bb = brown eyes

2 of the same allelesHomozygous

2 different allelesHeterozygous

homozygous dominanthomozygous recessive

Regents Biology

Genetics vs. appearance There can be a difference between

how an organism looks & its geneticsappearance or trait = phenotype

brown eyes vs. blue eyesgenetic 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 eyesbb = blues eyesBb = brown eyes

BB

bb

Bb

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

Po

ssib

le f

emal

e e

gg

sX

BB

Bb bb

BbB

b

B b

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

X Y

X

X

XX

XY

XY50% female : 50% male

XX

Regents Biology

IN PEA PLANTS

Tall is dominant over short

TALL = ____

SHORT = ____

LET’S MAKE A CROSS!

TALL SHORTX

What do you need to know before you begin?

Regents Biology

TALL parentWhat 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 BiologyGENOTYPE _____ PHENOTYPE _______

_____% of the

offspring

or

___/4

will be…

Regents Biology

Genetics vs. appearance There can be a difference between

how an organism looks & its geneticsappearance or trait = phenotype

brown eyes vs. blue eyesgenetic 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

IA, IB, i IA & IB alleles are co-dominant

glycoprotein antigens on RBC IAIB = 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