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Biology 10 Lecture
Chapter 23 - Patterns of Gene Inheritance
I. Overview
A. Mendel’s Laws
B. Genetic Disorders
C. Beyond Simple Inheritance Patterns
II. Mendel’s Laws
A. DNA in chromosomes contain thousands of segments called _____
1. Genes in DNA direct the formation of ______in cells, thus determine inherited ______
2. Genes have specific ______sequences and are found in particular regions, called ______(sgl., locus), on a chromosome
3. ______are genes that control the same trait (e.g., eye color), and are found in the same loci on ______chromosomes.
4. Alleles are represented by paired ______(e.g., BB, Bb, bb)
a.______allele: gene that controls for a trait that is ______whether it’s paired with another dominant allele or with a recessive allele.
1) ______dominant has 2 of the same dominant alleles (e.g.: BB).
2) ______ has one dominant and one recessive allele (e.g.: Bb). An individual that is heterozygous for a trait is often called a ______of the trait.
b. ______allele: gene that controls a trait that is only evident if the allele is paired with another recessive allele.
1) Homozygous recessive has 2 of the same ______alleles (e.g.: bb).
B. Gregor ______(Austrian monk 1860): Father of ______
1. Experimented on pea plants and discovered that each pea plant trait is controlled by 2 “______” (alleles).
2. One factor was ______(e.g., yellow seeds) over the other, which was ______(e.g., green seeds).
3. His findings led him to formulate the _____ of segregation and independent assortment
C. Segregation and Independent Assortment of Chromosomes (and their alleles) occurs during ______.
1. Law of ______
a. Each pair of homologous chromosomes can align (assort) itself in ____ possible ways in ______I and does so independently of the other chromosomes.
b. All possible ______of homologues can occur in the gametes (sperm and egg).
c. This law is used when solving genetics problems involving alleles on ______pairs of homologous chromosomes
2. Law of ______
a. Each homologous pair of chromosomes has two ______for each trait.
b. The chromosomes and their alleles ______(separate) during ______I.
c. Each resulting gamete contains only ___ chromosome and its ______from each homologous pair.
d. Fertilization gives the new individual ___ alleles for each trait.
e. This law is used when solving _____trait genetics problems.
D. Inheritance of a ______Trait with alleles on same pair of homologous chromosomes (______Dominance). Terms:
1. ______ - type of genes an individual has for a particular trait(s) (e.g.: ___ = homozygous dominant, ___ = heterozygous, ___ = homozygous recessive).
2. ______ - physical or observable characteristics that result from the genotype (e.g.: widow’s peak vs continuous hairline).
3. Gamete Formation – because segregation of alleles occurs during meiosis, each gamete will contain only ___ of each type of allele.
4. Punnett Square- device used to determine the ______of possible genotypes and phenotypes of simple genetic crosses. Directions for creating punnett squares (Widow’s peak activity):
a. Determine ______of P (parental) generation and all possible ______in their gametes. W=widow’s peak, w=straight hairline.
b. For this exercise, assume both parents are ______(heterozygous=Ww), so each of their gametes would contain a dominant (W) or a recessive (w) allele].
c. Align all possible combinations of _____ vertically and ___ horizontally (or vice versa).
d. Merge egg & sperm alleles in converging squares, then determine probable proportions of ______and ______of children (F = filial generation).
e. Monohybrid cross always results in ___:__ phenotypic ratio of offspring.
f. Chance has no memory - each new child has the same ______of genotypes & phenotypes.
5. One Trait ______
a. Used to determine whether an individual with a ______phenotype is homozygous dominant or heterozygous by crossing with a homozygous ______individual.
b. No recessive phenotype offspring indicates that the parent is homozygous ______.
c. Any offspring with recessive phenotype indicates that the parent is ______
E. Inheritance of _____ Traits on Different Pairs of Homologous Chromosomes (Complete Dominance). Directions:
1. Determine parental ______(we’ll assume both parents are ______- WwSs x WwSs). W=widow’s peak, w=straight hairline; S=short fingers, s=long fingers.
2. Determine all possible ______combinations in gametes, remember that each gamete receives only ___ of each allele (e.g.: ___, ___, ___, ___).
3. Set up a Punnett Square with ___ squares.
4. Join ______from gametes in converging squares.
5. Determine ______ratio of offspring from resulting genotypes. (Dihybrid cross always results in 9:3:3:1 phenotypic ratio.)
III. Genetic Disorders (______) - Many human disorders are due to abnormalities of single allele pairs.
A. ______charts can determine if a disorder is inherited.
1. Males are represented by ______, females by ______.
2. Horizontal line between circle & square represents a ______.
3. Vertical lines extend down to ______from union.
B. Autosomal ______Genetic Disorders
1. Caused by a ______ allele on an autosomal (not sex) chromosome.
2. A child and at least one ______is affected.
3. Example: ______’s Disease
a. Result of an abnormal gene on chromosome __.
b. Disease does not usually develop until ______age.
c. Causes degeneration of ______cells; person gradually loses control of muscle function and dies.
4. Do Punnett square of autosomal dominant disorder.
C. Autosomal ______ Genetic Disorders
1. Disorder is only present if both alleles for the trait are ______ on homologous chromosomes.
2. Parents are usually heterozygous ______ of a recessive gene.
3. Homozygous recessive ______is affected but parents are not
4. Example: Phenylketonuria (____)
a. Result of abnormal gene on chromosome ___.
b. Caused by lack of enzyme to break down ______(an amino acid).
c. ______accumulate in blood & urine.
d. Newborns are routinely tested for ____ in hospitals.
e. Diet low in ______can prevent mental retardation.
5. Do Punnett square PKU practice problem.
IV. Beyond Simple Inheritance Patterns
A. ______Inheritance
1. Controlled by two or more sets of ______, often on different pairs of homologous chromosomes.
2. Different alleles may have an ______effect on the trait.
3. Example: skin ______.
a. Couple with dark and light skin have ______skin color children.
b. Couple with medium brown skin color have children with skin colors from ______to ______.
4. Polygenic Disorders include ______, diabetes, hypertension, and many others.
B. ______Alleles
1. Within a population, there may be __ or more alleles that affect the same trait.
2. Each person still has only ___ of the alleles for the trait.
3. Example: _____ Blood Types
a. Type __ has __ antigen on RBC surface and antibodies against __ antigen; alleles are AA or AO (A is dominant).
b. Type __has __ antigen on RBC surface and antibodies against __ antigen; alleles are BB or BO (B is dominant).
c. Type ___ has __ & __ antigens on RBC surface and no antibodies against __ or __; alleles are AB (codominant).
d. Type __has no ______on RBC surface, but has ______against A & B antigen; alleles are OO (recessive alleles).
e. Do Punnett square on how to determine blood type.
4. ___ Factor
a. Inherited separately from ____ blood types.
b. Rh+ has ______on RBC surface, Rh- does not.
c. If Rh- woman marries Rh+ man, fetus may be ___.
d. Rh- mother exposed to Rh+ fetus’ blood builds up ______against Rh+ blood.
e. If subsequent baby is Rh+, mother’s ______can cross placenta and destroy the fetus’ RBCs.
C. Incomplete & Codominance
1. Occurs when neither member of an allelic pair is ______over the other.
2. ______ - both alleles are expressed equally (e.g.: __ blood type).
3. ______Dominance– heterozygous genotype has an ______phenotype between the dominant and recessive. Example: ______Cell Anemia
a. A defective gene produces abnormal ______(Hb), the oxygen-carrying protein in RBCs, so they assume a ______shape and clog arteries.
b. Genotype HbSHbShas full blown ______cell disease.
c. Genotype HbAHbA has ______hemoglobin.
d. Genotype HbSHbA (heterozygous) has the sickle cell _____ (a mild form of the disease).
e. Sickle cell anemia more prevalent among persons from Africa, where ______is prevalent.
f. Sickle cell trait protects RBCs from effects of malaria, thus large numbers of ______are preserved in the population.