Transcript Tt Tt - Issaquah Connect

Genetics “I can…” Review - 1
• Describe the difference between an offspring from
asexual reproduction and one from sexual reproduction.
• Include:
– How each genetically relates to the parents
– How many parents each have
– How is a clone like a identical twin? How is it different?
Genetics “I can…” Review - 1
• Describe the difference between an offspring from asexual
reproduction and one from sexual reproduction.
–In sexual reproduction the offspring are a combination of the
traits of the two parents. Offspring get exactly half of their
genetic information from each parent.
–In asexual reproduction the offspring are an exact copy of the
one parent.
–Identical twins are copies of each other, clones are copies of the
parent nucleus.
–Clones are similar to identical twins because they are genetically
identical.
Genetics “I can…” Review - 2
• Bob, a corn farmer was confused.
When he crossed a tall corn plant
and a short corn plant, (hoping to
get medium plants) he got all tall
plants. Explain to Bob why he got
the results he did.
• Make sure you use all the words
below correctly in your explanation.
homozygous heterozygous dominant
recessive phenotype genotype
Genetics “I can…” Review - 2
Tall – TT
Short- tt
t
t
T
T
Tt
Tt
Tt
Tt
Bob probably mated a
homozygous short plant
with a homozygous tall
plant. The results were 4
plants who had a
heterozygous genotype
and the phenotype of tall.
Tall seems to be the
dominant trait and short is
the recessive trait.
Genetics “I can…” Review - 3
• If Bob crossed the
heterozygous offspring of
his first generation plants,
what is the probability of
getting tall plants, medium
plants and short plants in
the next generation.
– Show how you know
• What is the ratio of tall
plants to short plants?
Genetics “I can…” Review - 3
Tall – Tt
Tall- Tt
T
t
T
TT
Tt
t
Tt
tt
¾ (75% chance) tall
¼ (25% chance) short
0/4 (0% chance) medium
(this scenario would need to be
incomplete dominance to have
medium as an option)
Ratio of dominant to recessive is 3:1
Genetics “I can…” Review - 4
• Identify the
dominance
pattern in each
trait as:
– simple
dominance
– incomplete
dominance
– co-dominance
Incomplete = blending of
two traits
Co = both traits are present
Characteristic
Genotype
Phenotype
Hair color
BB
Bb
bb
Brown
Brown
Blonde
Pinkie
DD
Dd
dd
Bent
Bent
Straight
Skin color
GG
GH
HH
Green
Green/Red striped
Red
Toe Length
TT
Tt
tt
Long
Medium
Short
Claw shape
CC
Cc
cc
Curved
Slightly Bent
Straight
Tooth length
LL
LS
SS
Long
Long and short
Short
Tail Spikes
AA
Aa
aa
Pointed
Pointed
Rounded
Eye color
EE
ER
RR
Green
One Green/One Red
Red
Genetics “I can…” Review - 5
Tt
What is the diagram to the right
Tt
called, how is it used and why is it
important?
• Label all the genotypes possible
Bob
• Determine if the condition is
tt
dominant or recessive
Tt
TT/
Tt
tt
• What is the genotype of Bob?
This is a Pedigree. It is used to study
heredity in humans – the passing
down of traits from one generation
to the next. Each pedigree
represents a single trait.
Tt
tt
tt
tt
The condition (trait) is
dominant
Genetics “I can…” Review - 5
In a pedigree:
•
Spouses are connected by horizontal lines
•
Offspring are connected to their parents
Tt
Tt
by vertical lines
•
Circles = female; squares = male
•
The shaded trait is the trait you are
Bob
following
•
You cannot determine which trait is
tt
Tt
dominant simply by counting how many
TT/
Tt
tt
are shaded and how many are not.
This is a Pedigree. It is used to study
heredity in humans – the passing
down of traits from one generation
to the next. Each pedigree
represents a single trait.
Tt
tt
tt
tt
The condition (trait) is
dominant
Genetics “I can…” Review - 6
Describe Fertilization in terms of genetics
• Include
– What is fertilization?
– What type of cells are involved?
– How many chromosomes are in each step?
– How is gender determined?
Genetics “I can…” Review - 6
Describe Fertilization in
terms of genetics
• Fertilization occurs when the
nucleus of an egg cell joins
the nucleus of a sperm cell
(sex cells).
• Each sex cell contains 23
chromosomes, which
combine to make 23 pairs (46
chromosomes).
• Eggs carry an X chromosome
and sperm carry an X or a Y.
XX=Female, XY=Male
Genetics “I can…” Review - 7
Describe the basic structure and function of DNA
• Include
– The physical structure (What it looks like)
– Where it is located
– The role it plays in living organisms
Genetics “I can…” Review - 7
Describe the basic structure and function of DNA
• Include
– It is in the shape of a twisted ladder (double helix). It is
made of a backbone and rungs (base pairs).
– Chromosomes are made up of DNA and are stored in the
nucleus of eukaryotic cells. Each segment of DNA that
codes for a certain characteristic is called a gene.
– DNA is the genetic blueprint for the phenotype of an
organism.
Genetics “I can…” Review - 8
Directions: Use the graphic below to organize your thoughts as
you form an explanation for the question below. You must
provide a written description as well as circling the answer you
believe is correct.
• Which of the following would complete
the missing base pairs from the DNA
molecule to the right? Explain.
a.
b.
c.
d.
AGCCTGCTA
TAGCAGGCT
ATCGTCCGA
TCGGACGAT
Genetics “I can…” Review - 8
Directions: Use the graphic below to organize your thoughts as you
form an explanation for the question below. You must provide a
written description as well as circling the answer you believe is
correct.
• Which of the following would complete the
missing base pairs from the DNA molecule
to the right? Explain.
b. TAGCAGGCT
In the DNA molecule, each chemical base
can only pair with one other. A always pairs
with T and G always pairs with C. Going
from top to bottom, that would make the
missing set of base pairs be TAGCAGGCT
Genetics “I can…” Review - 9
What makes you who you are?
In the Nature vs. Nurture debate,
scientists currently think that both the
way you were raised (nurture) and your
genetics (nature) play a role in what you
look like and the person you become.
Studying twins has been a big help in
determining which traits are inherited
(genetic) and which are acquired based
on your environment.