Presentation 9

What is genetics

The branch of biology focused on genes, heredity, and variation in living organisms.

Two types of genetic study

• Mendelian

• Molecular

What is Mendelian Genetics

The study of inheritance and sharing of traits at a personal level

What is Molecular Genetics

The study of inheritance and sharing of traits at a molecular level

Who is Gregor Mendel 

A “holy man” who established the foundational principles of heredity through experiments with pea plants

What are Mendel’s laws 

• Law of Unit Factors

• Law of Segregation 

• Law of Dominance 

• Law of Independent Assortment 

What is the Law of Unit Factors

The principle that traits are determined by discrete units (genes) that come in pairs, with one allele inherited from each parent

What is a “Unit Factor”

A gene

What is the Law of Segregation 

During formation of gametes, the two alleles responsible for a trait separate from each other making offspring with one allele from each parent

What is the Law of Dominance (33% Wrong)

When an individual has two different alleles for a trait, one allele may mask the expression of the other, resulting in only the dominant trait being observed in the phenotype.

What is a phenotype

The observable physical or biochemical characteristics of an organism

What is a genotype

The genetic representation of the alleles inherited from both parents that determines potential traits

What are dominant traits

Traits that tend to be expressed

What are recessive traits 

Traits that tend not to be expressed

What is the Law of Independent Assortment (100% Wrong)

Alleles for different traits segregate independently of one another during the formation of gametes, leading to genetic variation in offspring.

FOUR SLIDES BEFORE THIS

FOUR SLIDES BEFORE THIS

What is simple dominance

When a dominant allele and recessive allele are present, the dominant allele is expressed in the phenotype

What is Codominance

When both dominant and recessive alleles are expressed in the phenotype

What is incomplete dominance

When both dominant and recessive alleles are present, both alleles are incompletely expressed

What is an x linked trait

Chromosome attached to an x chromosome

How many genes are in an x chromosome

1000 working genes

What do x chromosomes code for

Traits such as color vision, female reproduction, blood type, and certain genetic disorders

How many genes are in a y chromosome

80 working genes

What do y chromosomes code for 

What is a Punnett Square

Tool used to model mating outcomes, finding genotype and phenotype

Steps of Punnett square

• Identify male genotype

• Identify sperm types possible

• Sort possible sperm types on one side 

• Identify female genotype

Two types of crosses

• Monohybrid

• Dihybrid

What is a monohybrid cross

A Punnett Square that examines on trait where there are four possible outcomes

Percent chance of each Monohybrid outcome

25% [percent] 

What is a dihybrid cross

A Punnett Square that examines two traits where there are 16 possible outcomes

What does a genotypic ratio communicate 

The homozygous [dominant or recessive] and heterozygous combinations of alleles in offspring.

What does a phenotypic ratio communicate

The possible expressed dominant homozygous and heterozygous combinations of alleles in offspring

How many alleles represent blood type 

Three alleles, unlike most genes which have only two

Three possible alleles in blood type

• I^A

• I^B

• i

Type A blood

• I^AI^A

• I^Ai

Type AB blood

• I^AI^B

Type B blood 

• I^BI^B

• I^Bi

Type O blood

• ii

What is RH factor

The positive or negative aspect of blood type

What blood type is the universal doner

Type O blood is

What blood type is the universal recipient

Type AB blood is

What is blood transfusion

The process of transferring blood from one person into another's bloodstream

What is a paternity test

Test using blood of both parents and child, making a Punnett Square, and evaluating outcomes to find possible paternity

How many chromosomes do we have

23 different chromosomes

What chromosome set

What are autosomes

Chromosome pairs 1-22

Human traits can be…

• Autosomal Dominant 

• Autosomal Recessive

• X-Linked

Types of human genetic assessments

• Pedigree Chart

• Karyotyping

• Amniocentesis

• Chorionic Villi Sampling

• Genetic Markers in Blood

What is a Pedigree Chart

A diagram that shows the occurrence and appearance of phenotypes of a particular gene in organisms and their ancestors over time and generations

Features of Autosomal Dominant Disorder on Pedigree Chart

• Generations are not skipped

• Males and Females affected equally

• Affected parent will have affected offspring

Features of Autosomal Recessive Disorder on Pedigree Chart

• Generations might be skipped

• Males and females affected equally

• Unaffected parents can have affected offspring

• Two affected parents will have affected offspring

Features of X-Linked Disorder on Pedigree Chart

• Generations can be skipped

• Males more than females

• Affected male inherits from mother

• Affected offspring may not have affected parents

What does Karyotyping determine

Test that determines extra, missing, or damaged chromosomes

What is Amniocentesis and Chorionic Villi Sampling

Ways to gather fetal cells for genetic testing to determine chromosomal abnormalities or genetic disorders. Does bring much risk for miscarriage or deformity

When should Amniocentesis be done 

After 16 weeks 

When should Chorionic Villus be done

Between 10 and 13 weeks

What are genetic markers

Proteins found in the blood that after testing can determine presence of specific genes