Genetics unit

What is genetics?

Genetics is the study of how traits are passed on from parents to offspring. It can also be called inheritance or heredity.

Traits are passed on through either ________ or ________

Sexual, asexual

What is a gene?

A complete message in the DNA. A single gene could code for your hair colour or the shape of your ear.

Humans have ____ chromosomes and many hundreds of thousands of genes, so each chromosome must contain thousands of genes.

46

Earth is estimated to be about ________ billion years old.

4.6

What is an allele?

The word used to describe the different versions of a gene for a particular trait.

What are examples of alleles for the trait of eye colour?

Brown, blue, green

What is a phenotype?

The set of physical characteristics of an organism inherited from the genes inherited from one's parents.

What are examples of phenotypes?

Curly hair, Type O blood, and the ability to roll one's tongue.

What is a genotype?

These are the actual genes inherited from one's parents.

One copy of each chromosome is inherited from each parent. This means that there are ____ genes for every trait in your body

Two

These genes are represented by ________ of letters such as AA, Bb, or dd.

Combo (combinations)

What is a dominant gene?

In each pair of genes, there is usually a stronger gene that can hide the effect of the weaker gene. The stronger gene is called the dominant gene and is always given a capital letter.

What eye colour is dominant in humans?

Brown eyes are considered dominant to blue eyes.

What is a recessive gene?

This is the weak gene in a pair of genes. It is given a lowercase letter and can be hidden by a dominant gene.

What does homozygous mean?

When both genes in a pair are the same.

Give examples of homozygous dominant and homozygous recessive alleles.

Homozygous Dominant: BB; Homozygous Recessive: bb

What does heterozygous mean?

When the genes in a pair are different. An organism with a pair of heterozygous genes is said to be hybrid for that trait.

What is a Punnett square?

A Punnett square is a tool used to predict the genetic outcomes of offspring in genetic crosses. It was created by Reginald Punnett, who helped explain how traits are inheritance from parents.

The square shows all possible ________ of parental alleles. It helps determine the chances of different ________ appearing in the offspring.

Combinations, phenotypes

If you cross a homozygous dominant male rabbit (Black fur, BB) with a heterozygous female rabbit (Black fur, Bb), what are the genotype and phenotype percentages of the offspring?

Genotype: BB = 50% (2/4), Bb = 50% (2/4)

Phenotype: Black fur = 100%, White fur = 0%

In cabbage butterflies, White wings (W) are dominant to yellow wings (w). If a heterozygous butterfly (Ww) is crossed with a homozygous recessive butterfly (ww), what are the percentage chances for each genotype and phenotype? A:

Geno type: Ww = 50% (2/4), ww = 50% (2/4)

Phenotype: White wings = 50%, Yellow wings = 50%

Genetic research helps us understand how certain genes or groups of genes cause ________ ________. This can help promote health and prevent disease.

Genetic disorders

Animal breeders may use genetic knowledge to improve the ________ of their animals. Plant breeders use genetic knowledge to create better crop ________ that may tolerate poor soil conditions, withstand pests, or grow faster.

Traits, varieties

Who is known as the "Father of Genetics" and when did his work begin?

The science of genetics began in 1850s with the work of the Austrian monk Gregor Mendel.

What did Gregor Mendel spend eight years conducting experiments on?

Pea plants. He kept detailed records of the traits of parental plants and offspring.

Analysis of Mendel's records revealed the ________ ________ that formed the basis for modern genetics!

Genetic laws

State the definition of the Law of Segregation.

The Law of Segregation states that each trait has two alleles (versions of a gene), one from each parent. During reproduction, these alleles separate, meaning they separate, so that each parent passes only one allele to the offspring.

State the definition for the Law of Independent Assortment

According to the Law of Independent Assortment, traits are passed on independently of each other. This means that the inheritance of one trait, like hair colour, does not affect the inheritance of another trait, such as eye colour.

State the defintion of the Law of Dominance.

The Law of Dominance explains that some alleles are dominant and can hide the effects of weaker, recessive alleles. If a dominant allele is present, it will appear in the offspring's traits, while the recessive allele will only appear if there is no dominant allele present.

How do we get different traits?

We inherit one copy of each genes from each parent, which can be different versions, known as alleles. This leads to a variety of traits.

The combination of different alleles from our parents creates unique traits in each of us, which is why ________ can look different from each other.

Siblings

What is a karyotype?

A karyotype is an arrangement of all the chromosomes in a cell, arranged in their homologous pairs.

Karyotypes can be used to ________ the number of chromosomes and to look for abnormalities.

Count

In human body cells (somatic cells), there are a total of ____ chromosomes arranged into ____ pairs.

46, 23

In human body cells, these cells are ________ (2n). In each pair of homologous chromosomes, one chromosome comes from the person's ________ and the other comes from the person's ________.

Diploid, mother, father

In human ________, only one chromosome from each homologous pair is present. These cells are ________ ($n$).

Gametes, haploid

In a human karyotype, we classify the pairs of chromosomes into two categories: ________ are the first 22 pairs of chromosomes, and ________ ________ are the 23rd pair of chromosomes and are the only pair that can be different.

Autosomes, Sex chromosomes

What are the two kinds of sex chromosomes, and what are the typical combinations for people with ovaries vs. people with testes?

The two kinds are X and Y.

People with ovaries typically have two X chromosomes (XX).

People with testes typically have an X and a Y chromosome (XY).

What is a sex-linked trait?

Sex-linked traits are caused by genes that are located on the X or Y chromosome. Remember that every chromosome contains many genes.

Most sex-linked traits are ________. This usually means that a person needs ____ copies of the recessive gene to inherit the trait.

Recessive, 2

Most sex-linked traits are found on the ____ chromosome. This is because the X chromosome is physically ________ than the Y chromosome—there is just more room!

X, larger

Why are individuals with the genotype XY or X0 much more likely to inherit sex-linked traits?

Since these individuals only have one X chromosome, a single recessive gene on the X chromosome is enough to cause the trait.

What are four common examples of sex-linked traits?

• Red-green colour blindness

• Hemophilia

• Duchenne muscular dystrophy

• Male pattern baldness

An individual who has one copy of a recessive allele for a genetic trait or disorder, but does not show symptoms of the trait or disorder is called a ________.

Carrier

What is a pedigree?

A pedigree is also called a family tree. It is a chart that can be used to represent patterns of inheritance between parents and offspring in a family.

What are the standard symbols used in a pedigree chart?

Male-Identifying: Square

Female-Identifying: Circle

Gender neutral: Triangle

What is Incomplete Dominance

A situation in which one allele is not completely dominant over another allele. The heterozygous phenotype is a blend of the two homozygous phenotypes.

What is an example of Incomplete Dominance?

A cross between a homozygous red flower (RR) and a homozygous white flower (WW) produces heterozygous pink flowers (RW).

What is Codominance?

A situation in which both alleles for a gene are expressed equally in the phenotype of a heterozygous organism. Both traits appear together without blending.

What is an example of Codominance?

In certain varieties of chickens, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens have a mixture of black and white feathers (called "erminette").

What are Multiple Alleles?

A series of three or more alternative forms of a gene, only two of which can exist in any individual.

What is a classic human example of Multiple Alleles?

ABO Blood typing (involves three different alleles)

What are Polygenic Traits?

Traits that are controlled by the interaction of two or more genes. These traits often show a wide range of phenotypes.

What are examples of Polygenic Traits in humans?

Skin color, height, and eye color.

What is a mutation?

A mutation is a permanent change in the DNA sequence of a gene or chromosome.

Mutations can happen when DNA is being ________ during cell division, or they can be caused by environmental factors.

Copied (replicated)

What are mutagens?

Environmental factors that cause mutations in DNA.

What are three examples of common mutagens?

• Ultraviolet (UV) radiation (from the sun)

• Chemicals (like those found in cigarette smoke)

• X-rays and radioactive materials

What is a Gene Mutation?

A change that affects only a single gene. This usually happens when one or more base pairs (letters) in the DNA sequence are changed, added, or deleted.

What is a Chromosomal Mutation?

A change that affects the structure or number of entire chromosomes. This can involve large parts of a chromosome breaking off, flipping, or moving to a different chromosome.

Are all mutations harmful?

No. Mutations can be harmful, neutral (have no effect), or beneficial (helpful).

Give an example of a harmful mutation, a neutral mutation, and a beneficial mutation from your lesson.

• Harmful: Genetic disorders like Sickle Cell, Anemia.

• Neutral: A change in DNA that does not change the protein being made, or a mutation that causes a minor difference like a unique hair whorl.

• Beneficial: A mutation that gives an organism a new trait that helps it survive better in its environment (the basis for evolution).

How do scientists divide Earth's history into manageable chunks of time?

By using the Geologic Time Scale.

What are homologous structures?

Body parts in different organisms that have a similar structural design but may serve different functions, showing evidence of a common ancestor.

What is evolution?

The process of biological change by which populations become different from their ancestors over many generations.

What is natural selection?

The process by which organisms that are better adapted to their environment tend to survive and produce more offspring.

How do we learn about the history of life and how species responded to environmental changes over time?

By studying the fossil record.