Transcript Slide 1

Genetics
Heredity
Lesson 1
Do Now
Video: What are genes?
Inheritance of chromosomes
• Egg + sperm  zygote
meiosis
egg
zygote
sperm
fertilization
mitosis &
development
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
X
bb
Bb
BB
Bb
Bb
Where did the blue eyes go??
Bb
Genes affect what you look
like…
X
bb
Bb
Bb
Bb
bb
Why did the blue eyes stay??
bb
Genes affect what you look
like…
X
Bb
BB or Bb BB or Bb BB or Bb
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?
• Paired chromosomes have same kind of
genes
– but may be different alleles
eye
color
(blue?)
hair
color
eye
color
(brown?)
hair
color
In class assignment
• History and Terminology worksheet
Homework
• Determining your genes worksheet
Punnett Crosses
• Lesson 2
Do Now
Video: Where do your genes come from?
• Choose one of the genes from your
homework last night (tongue rolling,
dimples etc)
• Find your partners genes for the same
trait
• Using your genes and your partners
genes determine the genes of your
“offspring”
Traits are inherited as separate
units
• 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
1 from Mom
homologous chromosomes
1 from Dad
Making gametes
B
BB = brown eyes
bb = blues eyes
Bb = brown eyes
BB
B
b
bb
b
 brown is dominant over blue
 blue is recessive to brown
B
Bb
Remember meiosis!
b
How do we say it?
2 of the same
Homozygous
BB = brown eyes
bb = blues eyes
homozygous dominant
homozygous recessive
2 different
Heterozygous
Bb = brown eyes
B
BB
B
b
bb
b
B
Bb
b
Punnett squares
x
Bb
male / sperm
X
female / eggs
Bb
B
b
BB
Bb
Bb
bb
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
How were these
brown eyes made?
eye
color
(brown)
eye
color
(brown)
eye
color
(brown)
eye
color
(blue)
vs.
B
BB
B
Bb
B
b
In class assignment
• Genetics Practice 1: Basic genetics
Homework
• Basics Punnett Squares
Penny Genetics
Lesson 3
Lab Activity
Genetics
&
The Work of Mendel
Lesson 4
2007-2008
Do Now
• BrainPop: heredity
Gregor Mendel
• Modern genetics began in the mid1800s 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
Mendel’s work
Pollen transferred from white
flower to stigma of purple flower
• Bred pea plants
– cross-pollinate
true breeding parents
– raised seed & then
observed traits
– allowed offspring
to self-pollinate
& observed next
generation
all purple flowers result
self-pollinate
?
Mendel collected data for 7 pea traits
Looking closer at Mendel’s work
Parents
1st
true-breeding
true-breeding
X
purple-flower peas
white-flower peas
100%
purple-flower peas
generation
(hybrids)
100%
self-pollinate
2nd
generation
75%
purple-flower peas
25%
white-flower peas
3:1
What did Mendel’s findings
mean?
• Some traits mask others
– purple & white flower colors are separate
I’ll speak for
both of us!
traits that do not blend
• purple x white ≠ light purple
• purple masked white
– dominant allele
• functional protein
– affects characteristic
allele producing
functional protein
mutant allele
malfunctioning
protein
• masks other alleles
– recessive allele
• no noticeable effect
• allele makes a
non-functioning protein
homologous
chromosomes
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
X
P
Explain Mendel’s results using
…dominant & recessive
…phenotype & genotype
purple
white
F1
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
X
P
purple
white
F1
all purple
Pp
Punnett squares
Pp x Pp
1st
Aaaaah,
phenotype & genotype
can have different
ratios
generation
(hybrids)
%
genotype
male / sperm
female / eggs
P
p
PP
25%
75%
Pp
P
PP
%
phenotype
50%
Pp
Pp
p
Pp
pp
pp
25% 25%
1:2:1
3:1
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
Environment effect on genes
• Phenotype is controlled by
both environment & genes
Coat color in arctic
Human skin color is
influenced by both genetics fox influenced by
& environmental conditions heat sensitive alleles
Color of Hydrangea flowers
is influenced by soil pH
In class assignment
• Gene Expression
Homework
• Regents Practice Questions
Beyond Mendel’s Laws
of Inheritance
Lesson 6
2007-2008
Do Now
• Gregor 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
RR
WW
RW
• make 50% less color
RR
Rr
rr
Incomplete dominance
P
X
true-breeding
red flowers
true-breeding
white flowers
100% pink flowers
1st
100%
generation
(hybrids)
self-pollinate
25%
red
2nd
generation
50%
pink
25%
white
1:2:1
Incomplete dominance
RW x RW
male / sperm
female / eggs
R
R
W
RR
W
%
genotype
RR
RW
RW
%
phenotype
25% 25%
50% 50%
RW
RW
WW
WW
25% 25%
1:2:1
1:2:1
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
phenogenotype
type
A
B
AB
O
antigen
on RBC
antibodies
in blood
donation
status
AA or A i
type A antigens
on surface
of RBC
anti-B antibodies
__
BB or B i
type B antigens
on surface
of RBC
anti-A antibodies
__
AB
both type A &
type B antigens
on surface
of RBC
no antibodies
universal
recipient
ii
no 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 are 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
• Co-dominance and incomplete dominance
OR
• Genetics Practice 3
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
X
X
Y
Sex chromosomes
Sex-linked traits
• Sex chromosomes have other genes on
them, too
– especially the X chromosome
– hemophilia in humans
• blood doesn’t clot
X
X
– Duchenne muscular dystrophy in humans
• loss of muscle control
– red-green color blindness
• see green & red as shades of grey
X
Y
Sex-linked sex-linked
traits recessive
2 normal parents,
but mother is carrier
HY x XHh
H Xh
XHH
male / sperm
XH
XH
Y
XH
XH XH
XH Y
Xh
XH Xh
XhY
Y
XH
XH Xh
Xh
female / eggs
XH Y
Dominant ≠ most common allele
• Because an allele is dominant
does not mean…
– it is better, or
– it is more common
Polydactyly
dominant allele
Polydactyly
individuals are born with
extra fingers or toes
the allele for >5 fingers/toes
is DOMINANT & the allele for
5 digits is recessive
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)
In class assignment
• genetics_xlinked
Homework
• X-Linked Worksheet
Variations on a Human Face
• Variations Lab