Genetics: The Science of Heredity Coach Julien Team 7-2

Standard S7L3 Students will recognize how biological traits are passed on to successive generations. a.. Explain the role of genes and chromosomes in the process of inheriting a specific trait. c. Recognize that selective breeding can produce plants or animals with desired traits

Vocabulary Heredity- the passing of physical characteristics from parents to offspring Trait- a characteristic that an organism can pass on to its offspring through its genes Genetics-t he study of heredity Fertilization-the joining of sperm and egg Purebred- organism is the offspring of many generations that have the same trait

Gene- factor that controls a trait Alleles- different forms of a gene Dominant allele- trait always shows up in the organism when the allele is present Recessive allele- is hidden whenever the dominant allele is present Hybrid- organism that has two different alleles for a trait Probability- a number that describes how likely it is that an event will occur.

Punnett Square- chart that shows all the possible combinations of alleles that can result from a genetic cross. Phenotype- is the physical appearance of an organisms Genotype- an organism’s genetic makeup or allele combination Homozygous- an organism that has two identical alleles for the same trait Heterozygous- an organism with two different alleles for the same trait

Codominancce-the alleles are neither dominant nor recessive: both alleles are expressed in the offspring. Meiosis-the process by which the number of chromosomes is reduced by half to form sex cells (sperm & eggs). Messenger RNA-copies the coded message from the DNA in the nucleus, and carries the message to the ribosome in the cytoplasm

Transfer RNA-carries amino acids to the ribosome and adds them to the growing protein Mutation-any change in a gene or chromosome

Chromosomes are made up of Many genes joined together

A heterozygous organism has Two different alleles for a trait

Which nitrogen base in RNA is NOT part of DNA Uracil

An organism’s genotype is its Genetic make up

Where does protein synthesis take place? On the ribosomes in the cytoplasm of the cell

The different forms of a gene are called alleles

Which term refers to physical characteristics that are studied in genetics? phenotype

A mutation is harmful to an organism if it Reduces the organism’s chances for survival and reproduction

What is a mutation? Any change in a gene or chromosome

What do transfer RNA molecules do during protein synthesis? Carry amino acids and add them to the growing protein

What does messenger RNA do during protein synthesis? Copies the coded message from the DNA and carries it into the cytoplasm

The order of the bases along a gene determines the order in which Amino acids are put together to form a protein

What determines the genetic code? The order of nitrogen bases along a gene

When sex cells combine to produce offspring, each sex will contribute Half the number of chromosomes in body cells.

What happens during meiosis? Chromosomes pairs separate and are distributed into new sex cells.

Walter Sutton discovered that the sex cells of grasshoppers have Half the number of chromosomes found in the body cells.

What is the chromosome theory of inheritance? Genes are carried from parents to offspring on chromosomes.

Purebred chicken with white feathers is crossed with a purebred chicken that has black feathers. Each of their offspring has both black and white feathers. Why does this happen? The alleles for feather color are neither dominant nor recessive.

An organism’s physical appearance is its phenotype

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? 75%

What does a Punnett square show? All the possible outcomes of a genetic cross

What is the probability of producing a tall pea plant from genetic cross between two hybrid tall pea plants? Three in four

What is probability? A number that describes how likely it is that an event will occur

What does the notation Tt mean to geneticists? One dominant allele and one recessive allele

What does the notation TT mean to geneticists? Two dominant alleles

Scientists call an organism that has two different alleles for a trait a hybrid

Factors that control traits are called genes

In Mendel’s experiments, what proportion of the plants in the F2 generation had a trait that had been absent in the F1 generation? One fourth (1/4)

What did Gregor Mendel do to study different characteristics in his genetics experiments? He cross-pollinated plants.