Genetics PowerPoint #2
Co-Dominance and Blood-typing, Incomplete Dominance, Genetic Disorders and Karyotyping, Pedigrees and Genetic
InheritanceEnvironmental Influence,
Sex-Linked Traits
In this presentationSlides 3-4: Punnett Square
Slide 5-7: Co-Dominance and Blood-typing
Slide 8: Incomplete Dominance
Slide 9: Sex Linked Traits (X-Linked Traits)
Slides 10 & 12: Meiosis
Slides 13-25: Karyotypes and Genetic Disorders
Slides 26-27 :Pedigrees and Genetic Inheritance
Slides 28 & beyond: Assignments From EOC coach book
Monohybrid Cross(Punnett Square)
• Used to determine phenotype and genotype of offspring (F1 generation).
• Phenotype = physical (color, shape, appearance)• Genotype = gene or allele (Aa, AA, aa)• Dominant = trait always displayed (AA, Aa)• Recessive = trait always masked; only expressed when
homozygous (aa)
Allele MeaningAA Homozygous DominantAa HeterozygousAa Homozygous recessive
Monohybrid Cross (Punnett Square)
• Example: The trait for brown eyes is dominant to blue eyes (b). Show a cross between a parent (P1) with blue eyes, and a parent that is heterozygous for brown eyes.
B b
b Bb bb
b Bb bb
P1: Bb x bb
F1: 50% Bb (brown eyes), 50% bb (blue eyes)
Co-Dominance
• All traits are DOMINANT (no recessive; lowercase alleles)
• In co-dominance, both traits are expressed.• Red Fish(R) x Blue Fish (B) = Red/Blue Fish
Co-Dominance and Blood Typing
Blood Type Allele
A AA (dominant) or Ai (heterozygous)
B BB (dominant) or Bi (heterozygous)
AB AB
O ii
Always assume that in blood-typing, that the question is referring to the heterozygous allele (Ai or Bi), unless otherwise stated
Use the Punnett Square to determine blood type
Co-dominance andBlood Typing
• What do you think? Is it possible for a mother with Type A blood and a father with Type B blood to produce a child with Type O blood?
Yes, it’s possible!If both parents are heterozygous for the blood type
Incomplete dominance
• All traits are DOMINANT (no recessive; lower cased alleles)• In incomplete dominance, traits blend together.• Ex. Red flowers (R) x White flowers (W) = Pink Flowers
Sex-Linked Traits“X-Linked Traits”
• Affects the sex chromosomes (pair #23)• Most Sex Linked Traits affect the X chromosome.• Males are more affected by sex-linked traits because they only
have one X chromosome• Females are often carriers because they have two X chromosomes
Female Sex Chromosomes
XX(carrier)
Male Sex Chromosomes
XY(affected)
She has an extra X, so she’s safe He only has one X, so he has the disease
Meiosis• Makes Gametes (sex cells)• Divides adult chromosome number in half (haploid); so that
parents only pass 23 chromosomes to offspring.• Meiosis I: Homologous chromosomes
a) Crossing Over (swapping of chromosomes from mom & dad). Occurs in Prophase Ib) Law of Independent Assortment: states that alleles (genes) that you receive from your parents sort RANDOMLY; during Meiosis when your gametes are being made. The reason why you are genetically different, and look different from parents.c) Non Disjunction (chromosomes do not separate properly), adding one chromosome, causing Down Syndrome, Klinefelter’s, Turner Syndrome
• Meiosis II: Sister ChromatidsEnd result; four daughter cells with 23 chromosomes. Meiosis II and Mitosis are similar
Meiosis
Crossing Over
IIII
Four haploid daughter cells with 23 chromosomes
Chromosomes break apart, exchanging
genetic material
Two diploid daughter cells
with 46 chromosomes
Divides chromosomes number in half so there are only 23
chromosomes in gametes
23 mom + 23 dad = 46 you!
Events in meiosis
• Crossing Over: Occurs in Prophase I, where the chromosomes break, and exchange genetic material
• Why organisms look different than parents
• Non-disjunction: failure of chromosomes to separate properly, causing organism to have extra chromosome (Trisomy 21)
Karyotypes and Genetic Disorder
• Karyotypes are mapping of human chromosomes• A normal human karyotype has 46 chromosomes
(diploid), and 23 pair (haploid).• Chromosomes 1-22 are called autosomes.• The sex chromosomes are the 23rd pair• Males are XY; females are XX
Normal Male Karyotype (XY)
Male (XXY) Klinefelter’s Syndrome
Males have an extra X Chromosomes
Smaller genital region
Develops breasts
47 chromosomes total
Klinefelter Male
Female Down Syndrome Karyotype
Trisomy 21 (Down Syndrome)
Extra chromosome @ pair #21
Dow
n Syndrome (Trisom
y 21)
Female Turner Syndrome (XO)Female with 45 chromosomes total.
Missing and X chromosome.
Infertile
Does not go through puberty
Non-functioning reproductive organs
Female (Turner Syndrom
e) XO
Cystic Fibrosis
• Thick mucus in the lungs and digestive tract
• Mainly affects Caucasian population
• 1 in 28 Americans carries the trait.
• Caused by defective protein in cell membrane.
• Treated with special diet, and physical therapy.
Tay-Sachs Disease
• Caused by recessive trait
• An important enzyme (protein) is missing that breaks down lipids (fat) in the central nervous system.
• Fat (lipids) accumulates in the CNS causing damage
Sickle Cell Anemia
• Primarily affects the African-American Community
• Red blood cells are crescent shaped
• Pain in the extremities• Caused by Point
(substitution) mutation• Patients with SCA are
immune to Malaria
PKU (Phenylketonuria)
• Recessive disorder• Missing an enzyme that
converts the amino acid Phenylalanine into Tyrosine.
• Phenylalanine cannot be broken down by the body and causes damage to the CNS
• Patients treated with diet low in phenylalanine
• Phenylalanine is found in many diet sodas.
Huntington’s Disease• Degeneration of Nerve Cells
(neurons)• Cognitive impairment• Inability to focus• Muscle rigidity• No treatment• Death in 1-5 years• Neuron Apoptosis• (neurons die)
Pedigree Key
Male Female
Affected FemaleAffected Male
Marriage (Union)
Carrier
A pedigree is a mapping of genetic inheritance. A family tree of disease.
Pedigrees and Genetic Inheritance
Independent Assignment List• Green EOC Coach Book: COACH BOOKS DO NOT GO HOME!!!!!
Read each lesson, and answer the questions that follow. Write the question AND the answer! QUIZ GRADE. Due Tuesday, April 29th.
1) Lesson 20: The Structure and Function of DNA. Pp 142-147. Answer Questions 1-4 on page 146-7
2) Lesson 21: The Structure and Role of RNA. Pp 148-152. Answer questions 1-5 on page 153.
3) Lesson 22: Genetics: Pp 154-159. Answer questions 1-4 on page 161Lesson 23: Meiosis and Genetic Variation. Pp 162-165. Answer questions 1-4 on pg. 166
4) Lesson 25: Genetic Disorders. Pp. 172-175. Answer questions 1-3 on page 177
5) Lesson 26: DNA Technology. Pp 178-183. Answer questions 1-3 on page 185.
6) Chapter 4 Review: pp. 186-192; answer questions 1-18
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