Biology Exam Review: Genetics and DNA

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fertilization

process in sexual reproduction in which male and female reproductive cells join to form a new cell

allele

one or two more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

hybrids

the offspring of crosses between parents with different traits

genes

a sequence of DNA that codes for a protein and thus determines a trait

segregation

seperation of alleles during gamete formation

gamete

specialized cell involved in sexual reproduction

probability

the likelihood that a particular even would occur

Punnet squares can determine the gene combinations that might result from a genetic cross

...

homozygous

organisms that have two identical alleles for the same trait (TT or tt)

heterozygous

organisms that have two different alleles for the same trait (Tt)

phenotype

physical characteristics

genotype

genetic makeup

independent assortment

independent segregation of genes during the formation of gametes

incomplete dominance

cases in which one allele is not completely dominant over the over

codominance

both alleles contribute to the phenotype.

multiple alleles

genes that have more than two alleles

polygenic traits

traits controlled by two or more genes

Mendel's Principles

1. the inheritance of biological characteristics is determined by individual units known as genes. Genes are passed from parents to their offspring

2. In cases in which two or more forms of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive.

3.sexually reproducing animals have two two copies of each gene - one from each parent. They segregate from each other when gametes are formed.

4. Alleles from different genes usually segregate from each other.

homologous

chromosomes that each have a corresponding chromosome from the opposite-sex parent

diploid

a cell that contains both sets of homologous chromosomes

consist of two complete set of chromosomes and two complete sets of genes

haploid

containing only one set of chromosomes therefore containing one set of genes

meiosis

process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.

tetrad

structure containing 4 chromatids that form during meiosis

crossing-over (metaphase)

results in an exchange of alleles between homologous chromosomes and produces new new combinations of alleles

Thomas Morgan Hunt

Mendel's law of independent assortment still holds true but, chromosomes assort independently, not the genes.

gene map

a map showing the relative locations of each known gene on one of the chromosomes

nucleotides

composed of 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base.

nitrogenous bases

adenine, guanine, thymine, and cytosine

prokaryote

a unicellular organism having cells lacking membrane-bound nuclei

eukaryote

an organism with cells characteristic of all life forms except primitive microorganisms such as bacteria

base pairing

only certain hydrogen bonds can form between bases (adenine can only go with thymine and guanine can only go with cytosine)

chromatin

DNA that is tightly coiled around proteins

replication

a process in which each cell will have a complete set of DNA molecules

DNA Replication

1. the DNA molecule separates into two strands
2. it then produces two new complementary strands following the rules of base pairing

DNA polymerase

it joins individual nucleotides to produce DNA molecules. it helps to maximize the odds that each molecule is a perfect copy of the original.

RNA vs. DNA: The Difference

1. the sugar in RNA is ribose instead of deoxyribose
2.RNA is single stranded, therefore no double helix
3. Contains uracil instead of thymine

Types of RNA

messenger RNA, ribosomal RNA, and transfer RNA

mRNA

carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell

ribosomal RNA

type of RNA that makes up the major part of ribosomes

transfer RNA

transfers amino acids to the ribosome as it is specified by coded messages in mRNA

transcription

(genetics) the organic process whereby the DNA sequence in a gene is copied into mRNA

RNA polymerase

an enzyme that binds to DNA and separates DNA strands during transcription (unzips the DNA)

promoters

certain regions of DNA that RNA polymerase will bind to in order to split (unzip) the DNA

pleiotropy

A single gene having multiple effects on an individuals phenotype

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