Download Chapter 11 Genetics - Duxbury Public Schools

Chapter 11 Genetics
STATE FRAMEWORKS
3. Genetics
Central Concepts: Genes allow for the storage and transmission of genetic information. They are a set of instructions encoded in the nucleotide sequence of each
organism. Genes code for the specific sequences of amino acids that comprise the proteins characteristic to that organism.
3.1
Describe the basic structure (double helix, sugar/phosphate backbone, linked by complementary nucleotide pairs) of DNA, and describe its
function in genetic inheritance.
3.2
Describe the basic process of DNA replication and how it relates to the transmission and conservation of the genetic code. Explain the basic
processes of transcription and translation, and how they result in the expression of genes. Distinguish among the end products of replication,
transcription, and translation.
3.3
Explain how mutations in the DNA sequence of a gene may or may not result in phenotypic change in an organism. Explain how mutations in
gametes may result in phenotypic changes in offspring.
3.4
Distinguish among observed inheritance patterns caused by several types of genetic traits (dominant, recessive, codominant, sex-linked, polygenic,
incomplete dominance, multiple alleles).
3.5
Describe how Mendel’s laws of segregation and independent assortment can be observed through patterns of inheritance (e.g., dihybrid crosses).
3.6
Use a Punnett Square to determine the probabilities for genotype and phenotype combinations in monohybrid crosses.
Genetics- the scientific study of heredity.
Heredity- passing of genetic traits from parent to offspring.
Trait- any characteristic that can be passed from parent to
offspring.
The varied patterns of stripes on
Zebras are due to differences in their
genetic codes.
What are some of your traits?
Humans have controlled traits for years.
ex. Indians with corn, breeding of dairy cows.
Aristotle- pangenes in blood.
Bloodlines and Blood Relative.
Gregor Mendel
1822- 1884
*Became a priest and studied math and science at the
University of Vienna.
*Spent 14 years working in a monastery and teaching
at the high school.
*Was in charge of the monastery garden and carried
out his work on garden pea plants.
Plant Reproduction
A flower is the reproductive structure of a plant. It contains the
male and female sex organs which produce pollen and eggs by
meiosis.
Fertilization results in a zygote which is contained in a seed.
Mendel's Experiments
*Pea plants are easy to grow so he could study many generations.
*Self Pollenating
*Show several traits in contrasting forms. No blending inheritance.
What he did:
Mendel’s Experiments
Dominant Trait
Recessive Trait
F1 Generation
F2 Generation
Ratio
Red Flowers
White Flowers
All Red
705 Red/224 White
3.15 : 1
Smooth Seeds
Wrinkled Seeds
All Smooth
5474 Smooth/1850 Wrinkled
2.96 : 1
Yellow Seeds
Green Seeds
All Yellow
6022 Yellow/2001 Green
3.01 : 1
Inflated Pods
Constricted Pods
All Inflated
882 Inflated/299 Constricted
2.95 : 1
Green Pods
Yellow Pods
All Green
428 Green/152 Yellow
2.82 : 1
Axial Flowers
Terminal Flowers
All Axial
651 Axial/207 Terminal
3.14 : 1
Tall Stems
Short Stems
All Tall
787 Tall/277 Short
2.84 : 1
Mendel's Conclusions:
Vocab: alleles are different forms of a gene.
i.e. red flower allele and white flower allele
*Parent plants contain two alleles (genes) for each trait.
*Parent plants pass only one allele (gene) to their offspring. Therefore, gametes
contain only one gene for each trait.
Mendel's 3 Principles:
The Principle of Dominance: some alleles are dominant and others are recessive.
The Principle of Segregation: alleles for each trait segregate independently into
gametes. Dominant alleles get passed equally to
recessive alleles.
The Principle of Independent Assortment: alleles for one trait are sorted
independently of the alleles for other traits during
gamete formation.
Probability
Expected vs. Observed
Mendel's Experiments: Monohybrid Crosses
Test Cross- Allows you to determine the
genotype of an unknown phenotype.
Trait: Rabbit Fur Color
B=brown fur allele
b= white fur allele
If you have a brown furred rabbit, do you know its genotype for sure?
Incomplete Dominance (Blending Inheritance)
when a heterozygous genotype results in an intermediate phenotype.
There are no dominant nor recessive alleles.
Ex. Trait: Snap Dragon Flower Color
ALLELES
GENOTYPES
PHENOTYPES
R= red flower allele
RR
Red flowered plants
W= white flower allele
WW
White flowered plants
RW
Pink flowered plants
(incomplete dominance)
Cross a red flowered snap dragon with a white flowered snap dragon.
What are the genotypic and phenotypic ratios in the F1 generation?
Multiple Alleles and Co-dominance
Ex. Trait: Human Blood Types
ALLELES
GENOTYPES
PHENOTYPES
IA = Type A allele
IA IA and IA i
Type A Blood
IB = Type B allele
IB IB and IB i
Type B Blood
i = Type O allele
ii
Type O Blood
*multiple alleles (3) in
IA IB (co-dominance)
Type AB Blood
the population
Sex-linked or X-linked traits- genes that appear
on the X chromosome.
The color vision gene is located on the X chromosome.
B = Normal color vision allele
b = Color Blind allele
GENOTYPES
XB XB
XB Xb
Xb Xb
XB Y
Xb Y
PHENOTYPES
Normal Color Vision Female
Normal Color Vision Female (carrier)
Color Blind Female
Normal Color Vision Male
Color Blind Male
Sex-linked or X-linked traits- genes that appear
on the X chromosome.
The color vision gene is located on the X chromosome.
B = Normal color vision allele
b = Color Blind allele
GENOTYPES
XB XB
XB Xb
Xb Xb
XB Y
Xb Y
PHENOTYPES
Normal Color Vision Female
Normal Color Vision Female (carrier)
Color Blind Female
Normal Color Vision Male
Color Blind Male
Cross a normal color vision man with a normal color vision woman, whose father
was colorblind. What are the male and female genotypic and phenotypic ratios of
their children?
Dihybrid Crosses- crosses that involve two
traits.
Traits: Mendel's Pea Plant Height and Flower Color.
T = Tall Plant Allele
R = Red Flower Allele
t = Short Plant Allele
r = White Flower Allele
Cross a pure bred tall, purebred red flowered plant with a short plant
with white flowers.
F.O.I.L.-USED TO FIND ALL THE POSSIBLE COMBINATIONS OF ALLELES
FOR TWO TRAITS.