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