Patterns of Inheritance

Chapter 9

Introduction

n Look at parents and offspring

n Children ____________ the characteristics of the parents

n The characteristic most common in nature is called the _________ type.

Introduction

n Patterns of inheritance can be explained by the behavior of chromosomes during

n 1. ____________

n 2. Fertilization

Mendel

n Gregor Mendel

n Augustinian __________

n Lived in Brunn, Austria

n __________ of genetics

n Published first paper about genetics in 1866.

Mendel

n Studied peas because

n 1. Grow __________

n 2. Have relatively _________ life spans (1 yr)

n 3. Have numerous __________ characteristics

n 4. Mating of individuals can be _____________

Mendel

n He could

n 1. ___________ fertilize by covering plants with a bag

n 2. ___________ fertilize by dusting the carpals of one with the pollen of another.

n Found ___________ characteristics, each of which came in two distinct forms

n Example: Seed _________ (yellow or green)

Mendel

n _____________ cross: Crossing two plants with one of the characteristics (green seeded plant with yellow seeded plant)

n _________________ cross: Crossing two plants with two of the characteristics (I.e. green wrinkled seeded plants with yellow smooth seeded plants)

Mendel

n True breeding parents are called _________ generation.

n First generation of children (offspring) are the _______ generation.

n Second generation of offspring (mating of two f₁ generations) gives rise to ________ generation.

Mendel

n _______________: Units that determine heritable characteristics

n Pairs of genes separate during _______________ (gamete formation)

n Fusion of gametes (sperm and egg) during fertilization ____________ genes once again

Mendel’s Hypothesis

n 1. There are alternative forms of genes called __________.

n 2. For each characteristic, an organism has __________ genes, one from each parent (they may be same or different)

n 3. A sperm or egg carries only ____________ allele for each characteristics (they separate during meiosis)

Mendel’s Hypothesis

n 4. ___________________ allele is the one fully expressed (majority characteristic)

n _____________________ allele is not noticeably expressed (minority characteristic)

n _______________ letter is used for Dominant allele and _________________ letter is used for recessive

Mendel’s Experiment

n He crossed _____________ flowered peas with white flowered peas.

n First generation (p generation)

n PP x pp -----à Pp for F₁

n (all came out ____________)

n Second generation

n Pp x Pp -------à __________ purple and ___________ white (a close to 1 to 3 ratio)

Genetic Terminology

n ________________: Both alleles for a trait are same

n Homozygous dominant: (PP) it will ______________ show up.

n Homozygous recessive: (pp) it will show up _______________ (might skip a few generations)

n _________________: Members of the allelic pair are different

Genetic Terminology

n Heterozygous (Pp): The dominant shows up but organism is a ____________ of the recessive gene

n These genetic make-up are called ________________ (genes of an individual)

Genetic Terminology

n ________________ is the characteristic observed.

n Each allele is located on one of the _____________ chromosomes

n Alleles of a gene reside at the same area (called ________) on homologous chromosomes.

Independent Assortment

n Principle of independent ______________: Each pair of allele separates independently during meiosis

n It is revealed by tracking ________ characteristics at once.

n Mendel bred round yellow seeded plants (RRYY) with green wrinkle seeded pants (rryy)

n The first generation: ____________

Independent Assortment

n Second generation:

n RrYy x RrYy

n There are 4² = _________ possible combinations

n F₂ generation exhibited a ratio of ____________

n ___________ round yellow; 3 wrinkled yellow, 3 round green and 1 wrinkled green

Punnett square

n A ____________ square allows calculation of probability of genotype among offspring.

n 1. Determine the ____________ of parent

n 2. Sperm on _____________ column

n 3. Egg on _________________ column

n 4. Possibilities for children inside of _____________

Note!

n Genotypes that produce the same phenotypes are not always the __________

n RRYY, RrYy, RRYy and RrYY all give the __________ phenotype (round and yellow seeds)

Test Cross

n It involves crossing an unknown genotype (expressing the dominant phenotype) with the ___________ phenotype

n YY or Yy x yy

n If YY (homozygous dominant), then all offspring will show ______________ trait

n If Yy (heterozygous), then _____________% dominant and 50% _____________

Probability

n Remember!

n Chance has no ___________

n Probability that two or more independent events will occur together is the multiplication of their chances occurring _________________.

n When parent genotype is Ww, the chance of gamete carrying W is __________

Probability

n Chance of WW is ½ X ½ = _________

n Chance of Ww is ½ x ½ = ¼

n Chance of wW is ½ x ½ = _________

n Chance of ww is ½ x ½ = ¼

n Chance of dominant showing up is ¼ (from WW) + ¼ (from Ww) + ¼ (from wW) = ¾ or _________%

n Chance of recessive (ww) is ¼ or ___________%

Pedigree Charts

n Used to follow inheritance of traits in ____________ families.

n __________________ are shown by a square ~

n ________________ are shown by a circle ±

n It is used to make ______________ about future generations (in genetic counseling)

Genetic Disorders

n Many inherited disorders are controlled by a ____________ gene.

n Over 1000 traits are attributable to a single gene.

n Many characteristics are determined by simple dominant-recessive _____________

n Most disorders caused by a _____________ allele

Genetic Disorders

n Most people with disorders are born to normal ______________ parents (called carriers)

n Example: ________________________ (the most common lethal genetic disease in USA)

n Most common among _________________ (1 in 20 is carrier)

n Reason for laws forbidding marriage between first ______________

Genetic Disorders

n Some disorders are caused by _____________ alleles

n ___________ in how deadly they are

n Some are _______________ handicaps

n Example: Having ___________ fingers

n Some are lethal if ________________ but non-lethal as heterozygous

n Example: __________________ (dwarfism)

Genetic Disorders

n Other conditions are only lethal in _____________ adults (so it can be passed on to the next generation before condition __________ up)

n Example:

n __________________ disease (degeneration of nervous system)

n Starts after _____________ age

Fetal Testing

n I. _________________: Taking a sample of the amniotic fluid at 14-16 weeks

n Fluid contains living cells that can be _____________

n Used to determine _________ of chromosomes

n ________________ tests can be conducted on fluid itself to determine presence of certain genetic disorders

n Small chance of _____________

Fetal Testing

n II. _________________ villi sampling: It involves removing tissue from the fetal side of placenta at ____________ weeks

n The rapidly dividing cells can be _________________ and some biochemical tests can be performed

n Its chance of complications is ______________ than amniocentesis.

Fetal Testing

n III. _________________ imaging of the fetus provides a non-invasive view inside of the womb

n IV. ___________________: A needle thin viewing scope is inserted into the uterus and the fetus is observed

n It has a ______________ chance of causing complications

Variations on Mendel’s Ideas

n Inheritance of many genes follows _______________ dominant-recessive pattern

n However, others follow more _____________ patterns

n These patterns include:

Incomplete Dominance

n One allele is not _______________ dominant (in a heterozygote)

n Heterozygote exhibits characteristics ____________ between both homozygous conditions

n Example: ____________ color in cats, Human __________

n White flower + red flower à ____________ flower

Multiple Alleles

n Some traits are controlled by ____________ than two alleles in population

n Example: ___________ type

n There are _____________ possible alleles

n Each individual has two of these alleles

n They code for two ____________________ (act as antigens) on surface of red blood cells

Multiple Alleles

n If wrong kind of blood is transfused, recipient can develop ______________ to the carbohydrates on surface of red blood cells

n Type O has neither carbohydrates and is universal __________ but only can receive type _________ blood

Multiple Alleles

n Type AB is the universal _______________ (has both carbohydrates) and can receive all kinds of blood but can only give to other AB

n Type A has the carbohydrate _________ and can receive type A and O and can give to A and AB

n Type B is similar to A. Can receive B & O and can give to _______ and _________

Pleiotropy

n A single gene may affect many ____________

n Example:

n Gene that codes for abnormal hemoglobin that causes sickle cell ______________

n Crystallization of hemoglobin causes the blood cells to have ___________ shape

Pleiotropy

n This can cause:

n 1. _____________ down of red blood cells

n 2. _____________ of cells and clogging of small blood vessels

n 3. _______________ of the sickle cells in spleen

n These can cause organ ___________

Pleiotropy

n Only ______________ suffer from disease

n __________________ may see effects when oxygen levels are reduced (in high altitudes)

n Heterozygous are immune to _____________

n The most common inherited disease among ________________

Polygenic Inheritance

n A single characteristic may be influenced by ___________ genes

n Skin ________________ (color) is determined by how much melanin is produced by skin cells

n This might be controlled by _______ or 4 genes.

n So you can get ______________ in skin color

Chromosomal Inheritance

n Linked genes are located close together on the _______ chromosome

n Two genes tend to be inherited _____________ because they are so close to each other

n ___________ over produces new combination of alleles

Chromosomal Inheritance

n Occurs between the genes on _____________ pairs of the same chromosome during meiosis

n Geneticists use crossover data to _________ genes

n Crossover data are used to map the ___________ of genes on chromosomes

Sex-Linked Genes

n Remember:

n Males are _______

n Females are __________

n __________ gene found on Y chromosome initiates the development of testes

n It plays an important role in sex _________________

Sex-Linked Genes

n Some genes are carried on ___________ chromosomes

n Most sex-linked characteristics result from genes on the _______ chromosome

n Pattern _____________ is a sex-influenced trait

n It behaves as ___________ in females and as _______________ in males

Sex-Linked Genes

n Sex-linked disorders affect mostly __________

n Examples:

n Red-green __________________

n Duchenne ______________________

n Hemophilia

n Males have only one __________ chromosome, any _____________ trait will be exhibited

Sex-Linked Genes

n Most known sex linked traits are caused by genes on the ______ chromosome

n Females have ______ X chromosomes and only show the trait if they are homozygous ______________

n Males cannot pass sex-linked traits to _______________ (males get their Y chromosomes from their dads)