Chapter 4: Genetics: the Science of Heredity

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This is on section 1-4 of Chapter 4.

Heredity

passing of physical characteristics from parents to offspring.

Gregor Mendel

Father of Genetics; formed their foundation

trait

Each different form of a characteristic

Genetics

scientific study of heredity

fertilization

when egg and sperm join

purebred organism

offspring of many generations that have the same trait.

gene

factors that control a trait

alleles

differetn forms of a gene

How are an organism's traits controlled?

They are controlled by the alleles inherited from their parents.

Dominant allele

One whose trait always shows up in the organism when the allele is present.

recessive allele

hidden whenever the dominant allele is present.

hybrid

organism that hastwo different alleles for a trait

probability

number that describes how likely it is that an event will occur.

punnett square

a chart that shows all the possible combinations of alleles that can result from a genetic cross

phenotype

visible traits or physical appearance

genotype

genetic makeup

codominance

alleles are neither dominant nor recessive so they are both expressed in offspring

meiosis

process when the number of chromosomes is reduced by half to form sex cells

Stage: Before Meiosis

each chromosome in the parents are copied

Stage: Meiosis 1

chromosome pairs move to the center, separate, and pull the cell intro two cells. With half the number of chromosomes in each.

Stage: meiosis 2

The two new cells move and split into 4.

Stage: Meiosis end

four sex cells have been produced, with only half the number of chromosomes that the parent cell had at the beginning.

Four nitrogen bases

adenine, thymine, guanine, and cytosine

Genetic code

formeed by nitrogen bases along a gene. specifies the type of protein produced.

Protein syntheses

production of proteins. Uses the info from a gene on a chromosome to produce a specific protein. takes place in the cytoplasm of a cell.

Differences between RNA and DNA

RNA: has one strand, uses Uracil, and has Ribose. DNA: has 2 strands, uses thymine, and has Deoxyribose

Messenger RNA

copies the coded message from the DNA in the nucleus and carries it to the ribosome

Tranfer RNA

Type of RNA that transports amino acids to ribosomes. Reads the message

Trans. the code: 1

DNA molecule unzips between the bases to allow the RNA strand to match up and transfer genetic info from the DNA to the RNA.

Trans. the code: 2

Messenger RNA leaves the nucleus and attaches to a ribosome. The RNA provides the code to make a protein molecle.

Trans. the code: 3

Transfer RNA attaches to the messenger RNA. Transfer RNA "read" the message by pairing up to the messenger RNA. Messenger RNA carries amino acids that link in a chain.

Trans the code: 4

Protein molecule grows as each transfer RNA put the amino acid along the chain. The chain grows until they have enough and the the ribosome releases the completed protein.

mutation

change in gene or chromosome. can cause a cell to produce an incorrect protein.

Types of mutation

deletion, addition, substitution

Effects of mutations

can be harmful or helpful, depends on environment.

Flickr Creative Commons Images

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