Social Studies 8th Grade - Genetics

Gregor Mendel

Gregor Mendel

A young priest that worked in the garden at a monastery in Vienna. He's considered the "Father of Genetics" and has observed traits in thousands of pea plants.

Heredity

Passing of traits from parents to offspring.

Genetics

Scientific study of how traits are passed.

Trait

A distinguishing quality or characteristic of an organism. Genes determine this quality.

Gene

Factors that control traits and are located on chromosomes.

Allele

Different forms or variations of a gene. One is inherited from each parent. They can either be dominant or recessive.

Recessive

Masked or hidden if a dominant allele is present. They can be represented with a lowercase letter.

Dominant

Always seen if present. They can be represented with a capital letter.

Phenotype

Physical characteristics or visible traits.

Genotype

The genetic makeup of an organism, also seen as an allele combination.

Homozygous Dominant

Two capital letters (AA).

Homozygous Recessive

Two lowercase letters (aa).

Heterozygous

A capital and lowercase letter (Aa).

Hybrid

An organism that has two different alleles for a trait. This is also known as a heterozygous combination of alleles.

Punnett Squares

A chart that shows all possible combinations of alleles that can result from a genetic cross. They can be used to determine the probability of offspring's genotype from a particular genetic cross.

Probability

The likelihood that a particular event will occur.

Incomplete Dominance

The offspring's phenotype is a combination of the parents' phenotypes.

How is incomplete dominance and codominance different from the dominant/recessive pattern that Mendel saw in his experiments with peas?

Mendel saw that the dominant allele completely masked this recessive allele. With incomplete dominance, the recessive allele is not completely masked. The dominant allele only partially covers the recessive allele.

Codominance

When both alleles can be observed in an organism's phenotype.

Multiple Alleles

When there are more than 2 allele possibilities for a trait.

How many alleles can people carry if the trait is controlled by multiple alleles?

One from each parent.

Polygenic Inheritance

Multiple genes that determine the phenotype of an organism.

What are the 2 sex chromosomes that make a female?

XX

What are the 2 sex chromosomes that make a male?

XY

Chromosomes

A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Karyotype

A picture of all the chromosomes in a cell arranged in pairs.

Mitosis

The regular sequence of growth, development, and division that cells undergo is known as the cell cycle. It repairs damaged cells and allows the organism to grow.

Meiosis

The process that produces genetically unique sex cells, or gametes.

Sex-linked Traits

Traits that are controlled by genes located on the sex chromosomes, or the X and Y chromosomes. These traits are more common in males than in females.

Universal Donor/Recessive Blood Type

Blood type O

Universal Recipient

Blood type AB

Dominant Blood Types

Blood type A and B

Pedigree

A chart or "family tree" that tracks which members of a family have a particular trait. They are used by geneticists to tract conditions and diseases in families.

In a pedigree, what does an unshaded circle represent?

Normal Female

In a pedigree, what does a shaded circle represent?

Affected Female

In a pedigree, what does a half-shaded circle represent?

Carrier Female

In a pedigree, what does an unshaded square represent?

Normal Male

In a pedigree, what does a shaded square represent?

Affected Male

In a pedigree, what does a half-shaded square represent? (only in diseases unrelated to sex-linked traits)

Carrier Male

DNA

A molecule named deoxyribonucleic acid. It has a double helix structure, also called known as a twisted ladder.

mRNA

This type of RNA is known as messenger RNA. Its function is to act as an intermediary between the genetic information in DNA and the amino acid sequence of proteins.

tRNA

This type of RNA is known as transfer RNA. Its function is to serve as a link between the mRNA molecule and the growing chain of amino acids that make up a protein.

rRNA

This type of RNA is known as ribosomal RNA. Its function is to bind to mRNA and tRNA to ensure that the codon sequence of the mRNA is translated accurately into an amino acid sequence in proteins.

Transcription

The organic process whereby the DNA sequence in a gene is copied into mRNA.

Translation

The process by which mRNA is decoded and a protein is produced.

Mutation

A change in the nucleotide sequence of a gene. This causes the cell to produce an incorrect protein which results in a different physical trait or phenotype.

Codon Chart

A chart that details the various nucleotide combinations that create the 20 known amino acids.

__________________________ is considered the father of genetics.

Gregor Mendel

What is probability?

The likelihood that a particular event will occur.

What does a Punnett square show?

All the possible outcomes of a genetic cross.

If D represents the dominant allele of a gene, then __ represents the recessive allele.

d

What does the notation TT mean to geneticists?

Two dominant alleles.

In a cross between two hybrid Tt pea plants, ______ percent of the offspring will be Tt. Feel free to draw a Punnett square to help you answer this question.

50%

In guinea pigs black fur is dominant over white fur. If a homozygous black guinea pig (BB) is crossed with a homozygous white guinea pig (bb), what is the probability that an offspring will have black fur?

100%

Blood type is a good example of a trait that is determined by multiple alleles. What statement best describes how this works?

There are three alleles involved in blood type (A, B, and O). You as an individual carry two of these alleles which determines your blood type.

True/False: A and B are codominant to each other and O is recessive.

True

True/False: B and O are both recessive and A is dominant.

False

True/False: An individual with the blood type A can have the genotype AA or AO.

True

True/False: An individual with the blood type A must be AA.

False

In one family the mother is blood type A and the father is blood type B. They have a son that is blood type AB and a daughter that is blood type O. What are the genotypes of the parents?

The mom has to be AO and the dad has to be BO.

Francis Crick

Discovered the structure of DNA with James Watson.

James Watson

Discovered the structure of DNA with Francis Crick.

Rosalind Franklin

Used X-ray diffraction to discover the double-helical shape of DNA.