GeneticsGenetics

Do Now

• Hand in your Karyotyping Lab if you haven’t already!

• Take out the Video – What are genes question sheet?

• Read over the questions so you know what your looking for when your watching the video.

HeredityHeredity

Lesson 1Lesson 1

Do NowDo Now

Video: What are genes?

Inheritance of chromosomes• Egg + sperm zygote

egg

sperm

zygote

fertilizationmitosis &

development

meiosis

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?)

Effect of genes• Genes come in different versions

– brown vs. blue eyes– brown vs. blonde hair– alleles

Genes affect what you look like

XBBbb

Bb Bb Bb Bb

Where did the blue eyes go??

Genes affect what you look like…

XBbbb

Bb Bb bb bb

Why did the blue eyes stay??

Genes affect what you look like…

XBbBb

BB or Bb BB or Bb BB or Bb bb

Where did the blue eyes come from??

What did we show here?• 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

• Some alleles mask others– brown eye color masked blue

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

In class assignment

• History and Terminology worksheet

Homework

• Determining your genes worksheet

Punnett Crosses

• Lesson 2

Do NowCheck answers from last night’s

homework (& take out last nights homework)

Read over the questions on your sheet so you know what your are looking for in the video.

Video: Where do your genes come from?

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

Making gametes

BB = brown eyesbb = blues eyesBb = brown eyes

BB

bb

Bb

brown is dominant over blue

blue is recessive to brown

Remember meiosis!

B

B

b

b

B

b

How do we say it?

BB = brown eyesbb = blues eyes

Bb = brown eyes

2 of the sameHomozygous

2 differentHeterozygous

BB

B

B

bb

b

b

Bb

B

b

homozygous dominanthomozygous recessive

Punnett squaresBb x Bb

male / sperm

fem

ale

/ eg

gs

X

BB

Bb bb

BbB

b

B b

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

Genetics vs. appearance

eye color(brown)

eye color

(brown)

eye color(blue)

eye color

(brown)

vs.

BB

B

BBb

B

b

How were these brown eyes made?How were these brown eyes made?

In class assignmentIn class assignment

• Genetics Practice 1: Basic genetics

HomeworkHomework

• Basics Punnett SquaresBasics Punnett Squares

Penny GeneticsPenny Genetics

Lesson Lesson 3

Lab ActivityLab Activity

2007-2008

Genetics&

The Work of Mendel

Lesson 4

Do Now

• BrainPop: heredityBrainPop: heredity

• Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas– used good experimental design– used mathematical analysis

• collected data & counted them

– excellent example of scientific

method

Gregor Mendel

Pollen transferred from white flower to stigma of purple flower

all purple flowers result

Mendel’s work

?

self-pollinate

• Bred pea plants– cross-pollinate

true breeding parents– raised seed & then

observed traits– allowed offspring

to self-pollinate & observed next generation

Mendel collected data for 7 pea traits

2nd

generation

3:175%purple-flower peas

25%white-flower peas

Looking closer at Mendel’s work

Parents

100%1st

generation(hybrids)

100%purple-flower peas

Xtrue-breedingpurple-flower peas

true-breeding white-flower peas

self-pollinate

What did Mendel’s findings mean?

• Some traits mask others – purple & white flower colors are separate

traits that do not blend • purple x white ≠ light purple• purple masked white

– dominant allele • functional protein

– affects characteristic

• masks other alleles

– recessive allele • no noticeable effect• allele makes a

non-functioning protein

homologouschromosomes

allele producingfunctional protein

mutant allele malfunctioning

protein

Genotype vs. phenotype

• Difference between how an organism “looks” & its genetics– phenotype

• description of an organism’s trait

– genotype • description of an organism’s genetic makeup

Explain Mendel’s results using…dominant & recessive …phenotype & genotype

F1

P X

purple white

all purple

Making crosses

• Can represent alleles as letters– flower color alleles P or p– true-breeding purple-flower peas PP– true-breeding white-flower peas pp

PP x pp

PpF1

P X

purple white

all purple

Punnett squares

Pp x Pp

P pmale / sperm

P

p

fem

ale

/ eg

gs

PP

75%

25%

3:1

25%

50%

25%

1:2:1

%genotype

%phenotype

PP Pp

Pp pp pp

Pp

Pp

1st

generation(hybrids)

Aaaaah,phenotype & genotype

can have different ratios

In class assignment

• Simple Genetics Practice Problems

Homework

• Complete simple genetics practice for homework

Gene Expression

• Lesson 5

Do Now

• Directed Reading Activity: Gene Expression

• 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

Environment effect on genes

Coat color in arctic fox influenced by heat sensitive alleles

In class assignment

• Gene Expression

Homework

• Regents Practice Questions

2007-2008

Beyond Mendel’s Lawsof Inheritance

Lesson 6

Do Now

• Gregor Mendel Video: HeredityGregor Mendel Video: Heredity

Extending Mendelian genetics

• Mendel worked with a simple system– peas are genetically simple– most traits are controlled by single gene– each gene has only 2 version

• 1 completely dominant (A)• 1 recessive (a)

• But its usually not that simple!

Incomplete dominance

• Hybrids have “in-between” appearance– RR = red flowers– rr = white flowers– Rr = pink flowers

• make 50% less color

RR Rr rr

RR

WW

RW

Incomplete dominance

true-breedingred flowers

true-breeding white flowers

XP

100%

100% pink flowers1st

generation(hybrids)

self-pollinate

25%white

2nd

generation

25%red 1:2:1

50%pink

Incomplete dominance

R Wmale / sperm

R

Wfem

ale

/ eg

gs RR

RW WW

RW

25%

1:2:1

25%

50%

25%

1:2:1

%genotype

%phenotype

RR

RW

RW

WW

25%

50%

RW x RW

Codominance

• Equal dominance– human ABO blood groups– 3 version

• A, B, i• A & B alleles are codominant• both A & B alleles are dominant

over i allele

– the genes code for different sugars on the surface of red blood cells• “name tag” of red blood cell

Genetics of Blood type

pheno-type

genotypeantigenon RBC

antibodiesin blood

donationstatus

A A A or A itype A antigens

on surface of RBC

anti-B antibodies __

B BB or B itype B antigens

on surface of RBC

anti-A antibodies __

AB ABboth type A &

type B antigens on surface

of RBC

no antibodiesuniversal recipient

O i ino antigens on surface

of RBC

anti-A & anti-B antibodies

universal donor

Blood donation

clotting clotting

clotting clotting

clotting clotting clotting

One gene: many effects

• The genes that we have covered so far affect only one trait

• But most genes affect many traits – 1 gene affects more than 1 trait

• dwarfism (achondroplasia)• gigantism (acromegaly)

Many genes: one trait

• Polygenic inheritance– additive effects of many genes– humans

• skin color• height• weight• eye color• intelligence• behaviors

Human skin color

• AaBbCc x AaBbCc – can produce a wide

range of shades– most children =

intermediate skin color

– some can be very light & very dark

In class assignment

• Genetics Practice 3: Blood Types Genetics

Homework

• Finish Worksheets

Sex-Linked Genetics

Lesson 7

Do Now

• Review Genetics Practice 3 OR practice co dominance and incomplete dominance

Genetics of sex

• Women & men are very different, but just a few genes create that difference

• In mammals = 2 sex chromosomes – X & Y

– 2 X chromosomes = female: XX

– X & Y chromosome = male: XY

X Y

X X

Sex chromosomes

Sex-linked traits

• Sex chromosomes have other genes on them, too– especially the X chromosome– hemophilia in humans

• blood doesn’t clot

– Duchenne muscular dystrophy in humans• loss of muscle control

– red-green color blindness• see green & red as shades of grey

X Y

X X

Sex-linked traits

XH Ymale / sperm

XH

Xhfe

mal

e / e

gg

s XHXH

XHXh

XHY

XhYXHXh

XH

Xh

XHY

Y

XH

XHXH XHY

XHXh XhY

sex-linked recessive

2 normal parents,but mother is carrier

HH HhxXHY XHXh

Dominant ≠ most common allele

Polydactylydominant allele

• Because an allele is dominant does not mean…– it is better, or– it is more common

Polydactyly

recessive allele far more common than dominant only 1 individual out of 500

has more than 5 fingers/toes so 499 out of 500 people are

homozygous recessive (aa)

the allele for >5 fingers/toes is DOMINANT & the allele for 5 digits is recessive

individuals are born with extra fingers or toes

In class assignment

• genetics_xlinked

Homework

• X-Linked Worksheet

Variations on a Human Face

• Variations Lab