Download Biology, Chapter 10.1 Mendel 10.1 Mendel`s Laws of Heredity Why

Biology, Chapter 10.1
Mendel
10.1 Mendel's Laws of Heredity
Why Mendel Succeeded
Intro
Mendel chose his subject carefully
1. What characteristics of Pisum made it a good subject for Mendel's studies?
Reproduce _________________
Haploid male and female gametes fuse during ___________________________
Meiosis in anthers gives pollen, in ovules gives eggs
Easy to __________________________ for mating
Closed flowers most often self-pollinate
Can open the flowers, _________________________, and use separate pollen
Easy to grow; give many offspring per plant; many known traits
Mendel was a careful researcher
2. How did Mendel's application of the scientific method lead to success?
Performed ________________________________: studied one trait at a time, at first
_______________________ his experiments
Mathematically and statistically analyzed his data
___________________ his results
Mendel's Monohybrid Crosses
Intro
3. Contrast true breeding and hybrid peas.
___________________________ are genetically pure
Ex.: true breeding tall always gave tall
Ex.: pure bred dogs
____________ are the offspring of parents with contrasting traits
Ex.: the offspring of one ______ parent and one ___________ parent
Monohybrid means have one contrasting characteristic in the parents
The first generation
4. Exemplify Mendel's _____________________ crosses.
Parents: true breeding tall X true breeding short
F1 generation = first generation of offspring
F = "filial"
In the example, pure tall X pure short  ________________________
The second generation
Next cross: _______________ X ________________ from the F1
F2 generation: _______________________________________
The rule of unit factors
5. Differentiate genes and alleles and give examples.
Genes govern traits like plant height and flower color
___________ are forms of genes
Height gene; 2 alleles; tall and short
Flower ________ gene; 2 ________________; purple and white
The rule of dominance
6. Define dominant and recessive in terms of the behavior of alleles in crosses.
Dominant traits ________________________ recessive traits
Ex.: dominant tall covered up recessive short in the F1
Symbols
Dominant alleles are given a ____________ letter; T for tall
Recessive alleles are given the corresponding small letter; t for short
They are two forms of the same gene
The law of segregation
7. Summarize the law of segregation.
Each offspring gets _______ of each allele from ______________________
The ______________________ of alleles determines the trait
When the offspring reproduce one of its two alleles is given ________________
Phenotypes and Genotypes
8. Contrast genotype and phenotype.
______________ = the combination of alleles in an individual
_______________ = the appearance of the trait
9. Contrast homozygous and heterozygous.
________zygous = two alleles that are the ________; ex.: TT or tt
_________zygous = two alleles that are ________________; ex.: Tt
Mendel's Dihybrid Crosses
Intro
10. Exemplify Mendel's dihybrid crosses.
Parental: pure ______________________ X pure _____________________
The first generation
F1: __________________________________________________
The second generation
Next cross: round, yellow hybrid X round, yellow hybrid from the F1
F2 generation:
____ round, yellow
____ round, green
____ wrinkled, yellow
____ wrinkled, green
The law of independent assortment
11. Summarize the law of independent assortment.
Genes for different traits are ________________________________
For the above example: seed shape allele is independently from seed color allele
Mainly because the genes are on ___________________________________
Punnett Squares
Intro
Monohybrid crosses
12. For practice, draw and analyze Punnett squares for monohybrid crosses of:
Two heterozygous axial plants
Two heterozygous plants with yellow seeds
Two heterozygous six-fingered people
Two heterozygous people with free-hanging earlobes
Dihybrid crosses
13. For practice, draw and analyze Punnett squares for monohybrid crosses of:
Two heterozygous axial plants also heterozygous for yellow seeds
Two heterozygous six-fingered people also heterozygous for free-hanging earlobes
Probability
14. How did Mendel apply the laws of probability to predict the outcomes of individual and large groups
of crosses?
For monohybrid example
1/2 chance of getting dominant gene from the father
1/2 chance of getting dominant gene from the mother
1/2 X 1/2 chance of both happening to give homozygous dominant
For dihybrid example
1/4 chance an offspring will be homozygous recessive for one trait
1/4 chance an offspring will be homozygous recessive for the other trait
1/4 X 1/4 = 1/16 chance of the offspring being homozygous recessive for both traits
10.2 [continued from the previous test]
Meiosis Provides for Genetic Variation
Intro
Genetic recombination
15. Describe two sources of genetic recombination in meiosis.
_________________ switches alleles on homologous chromosomes
Parental chromosomes randomly align and separate in ____________________
Meiosis explains Mendel's results
16. Correlate the behavior of chromosomes with the behavior of Mendel's factors.
__________________ are in pairs, _______________ are in pairs
Chromosomes separate in anaphase I, factors separate in anaphase I
We inherit ________ of chromosomes, __________ of factors from each parent
Different pairs of homologues separate independently, same for factors
Nondisjunction
Intro
17. Define nondisjunction and some of its possible consequences.
= failure of chromosomes to _________________ properly in meiosis
Consequences
One extra chromosome [2n +1] = trisomy; ______________________
One less [2n -1] = _____________; Turner syndrome
Extra whole sets [3n] = __________________
Polyploidy
18. Differentiate the effects of polyploidy in animals and plants.
In animals, almost always ______________
In plants, polyploids are often ________________________________
Gene Linkage Maps
19. How does the behavior of genes on the same chromosome violate the law of
independent assortment.
Genes on the same chromosome are a ________________________
Part of the same DNA strand, tend to __________________________________
20. How is crossing over used to create chromosome maps.
__________________ separates genes on the same chromosome
The _________________ of separation is a measure of _____________
The closer two genes are the lower the frequency of crossing over
And, vise versa
Example: A-B, 5; C-B, 40; A-D, 25; C-D, 10
Draw map starting with longest interval  C-B, 40
Work from longest two shortest
Try out hypothetical arrangements
Chapter 12, Patterns of Heredity and Human Genetics
12.1 Mendelian Inheritance of Human Traits
Making a Pedigree
Pedigrees illustrate inheritance
1. List the rules for organizing a pedigree.
____________ = females, ____________ = males
Each row is a generation
Biological parents are connected by horizontal lines
Biological children are connected by a bracket under their parents
______________ individuals are shaded; ____________ half-shaded
Death is indicated by a slash
Analyzing a pedigree
2. List guidelines for recognizing simple patterns of heredity in a pedigree.
Rare recessives
_________________________________
People marrying into the family are assumed to not carry
Marriage ________________________ is a tipoff
Dominants ______________________
____________________ affects males usually exclusively
Simple Recessive Heredity
Intro
3. How significant are human recessive disorders?
Most genetic disorders are ______________________
Cystic fibrosis
4. Describe the prevalence, symptoms, and treatment of cystic fibrosis.
1 in 28 whites are ______________________; 1 in 2500 white babies has it
Defect in a plasma membrane protein  ________________________
Physical therapy, special diet, lung transplant
Tay-Sachs disease
5. Describe the prevalence, symptoms, and treatment of __________________ disease.
Most common in Jewish people from Eastern Europe
Lack a protein that ______________ brain lipids  early neural degeneration
Experimental therapies only: enzyme replacement, gene therapy
Phenylketonuria
6. Describe the prevalence, symptoms, and treatment of __________________________.
1 in 15,000 births; postnatal hospital testing in the US
Lack the enzyme to degrade phenylalanine;  _____________________
_______ low in phenylalanine completely ______________________________
Simple Dominant Heredity
Intro
Simple dominant traits
7. List common non-pathological human dominant traits.
Cleft chin, widow's peak, freely hanging earlobes, hitchhiker's thumb, mid-digital hair
Huntington's disease
8. Describe the prevalence, symptoms, and treatment of _____________________________.
10 in 100,000 births in Western Europe; 0.1 in 100,000 in Africa
___________________________; slow neural degeneration
Testing but little treatment
12.2 When Heredity Follows Different Rules
Complex Patterns of Intelligence
Incomplete dominance: Appearance of a third phenotype
9. Contrast the appearance of incomplete dominance with simple dominance and recessiveness.
Simple dominance and recessiveness: heterozygote looks like dominant homozygote
Incomplete dominance: heterozygote has an ___________________________________
10. Describe an example of incomplete dominance.
Snapdragon flower color: red = RR, white = R'R', pink = RR'
_____________________  all pink
____________________  1/4 red + 1/2 pink + 1/4 white
Codominance: Expression of both alleles
11. Contrast the appearance of codominance with simple dominance and recessiveness.
Simple dominance and recessiveness: heterozygote looks like dominant homozygote
____________________: heterozygote has both homozygote phentotypes side-by-side
12. Describe an example of codominance.
Chicken feathers [one gene]: white = WW, black = BB, checkered = WB
_________________________  all ____________________
Checkered x checkered  1/4 black + 1/2 checkered + 1/4 white
Multiple phenotypes from multiple alleles
13. Define and exemplify multiple alleles.
___________________ for a gene
Examples
Pigeon color
BA is red, B is blue, b is chocolate
BA is dominant to B is dominant to b
_______ blood type: IA and IB are codominant, i is recessive to both
Sex determination
14. How is sex determined in humans?
22 pairs of chromosomes look the same in both sexes = autosomes
One pair looks different = sex chromosomes
____ = female
____ = male
Sex-linked inheritance
15. How was sex-linkage discovered?
T.H. Morgan found _______________________________; it was male
He crossed it with a normal, re-eyed female
All of the offspring had normal eyes = the F1
He mated the F1 together
 in the F2 _____________________________________________________
Conclusion: eye color gene is on the ___________________________
16. Predict the outcomes of crosses involving sex-linked traits.
Ex.: white-eyed male x heterozygous red-eyed female
XrY x XRXr [no R gene on the Y chromosome]
Male gametes: 1/2 Xr + 1/2 Y
Female gametes: 1/2 XR + 1/2 Xr
Ex.: red-eyed male x heterozygous red-eyed female
Polygenic inheritance
17. Define polygenic inheritance and give examples of such traits.
= governed by _____________________; give a range of phenotypes
Traits: ________________, weight, ___________________
Environmental Influences
Influence of external environment
18. Give examples of external influences on phenotype.
Temperature affects _________________________________
Shapes of leaves are affected by the amount of sunlight
Influence of internal environment
19. Give examples of internal influences on phenotype.
Female sheep have slender curved horns; males are heavy coiled
_______________________________ is dominant in men, recessive in women
12.3 Complex Inheritance of Human Traits
Codominance in Humans
Sickle-cell anemia
20. How is sickle-cell expressed as a codominant trait? How is it recessive?
________ normal and sickle hemoglobins are made in the heterozygote
The anemia is _____________________
Disease is caused by receiving sickle allele from both parents
_________________________________ with "sickle-cell trait"
21. Draw and analyze the Punnett square for the marriage of two people with sickle-cell trait.
Multiple Alleles Govern Blood Type
22. List the phenotypes and genotypes for ABO blood type in humans.
___________ blood: IAIA or IAi
___________ blood: IBIB or IBi
___________ blood: IAIB
___________ blood: ii
The importance of blood typing
23. How is blood typing important in our society?
Medically: wrong blood is __________________ after transfusion
Evidence: can easily ________________ someone as a source or parent
24. Determine possible parentage give ABO blood types for prospective parents and children.
Can a type O child come from an A father and a B mother?
Can an A child have a type B father?
Can an AB mother and a type O father have a type A child?
Sex-linked Traits in Humans
Red-green color blindness
25. Predict the offspring of a red-green colorblind father and a mother heterozygous for redgreen color blindness.
Red-green color blindness is ____________________
Father is XcY; gametes are 1/2 Xc and 1/2 Y
Mother is XCXc; gametes are 1/2 XC and 1/2 Xc
Hemophilia: An X-linked disorder
26. Describe hemophilia and its treatment.
____________________________; missing a blood clotting factor
Purified ________________________ now completely control the condition
27. Predict the offspring of a normal father and a hemophiliac mother.
Father is XHY; gametes are 1/2 XH and 1/2 Y
Mother is XhXh; gametes are all Xh
Polygenic Inheritance in Humans
________________: A _____________________ trait
Changes in Chromosome Numbers
Abnormal numbers of autosomes
28. Describe a ___________________.
Photographs of chromosomes lined up in pairs
Used to detect chromosomal abnormalities
Down syndrome: Trisomy 21
29. Describe Down syndrome.
_________________; 1 in 700 births
Some retardation
Diagnosed in _______________________ and ultrasound
Abnormal numbers of sex chromosomes
30. Describe common abnormal numbers of sex chromosomes.
XO
45 total chromosomes; _____________________________
____________________________ with varying degrees of retardation
XXY
47 total; _______________________ syndrome
Sterile ______________________ males
XYY
47 total; 1 in 1000 boys
Boys with increased risk of ___________________________ and delayed
speech and language skills