Biology Semester 2 Final Review

Gregor Mendel

Father of genetics

Genotype

An organism's genetic makeup, or allele combinations.

Phenotype

An organism's physical appearance, or visible traits.

homozygous dominant

Both alleles (factors) for a trait are the same and dominant (AA)

heterozygous

An organism that has two different alleles for a trait

homozygous recessive

Both alleles (factors) for a trait are the same and recessive (aa)

principle of dominance

states that some alleles are dominant and others are recessive

Principle of Independent Assortment

states that genes for different traits can segregate independently during the formation of gametes

Allele

Different forms of a gene

Segregation

Separation of alleles during gamete formation

Gametes

sex cells

Probability

likelihood that a particular event will occur

Punnett Square

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

incomplete dominance

Situation in which one allele is not completely dominant over another allele

multiple alleles

three or more forms of a gene that code for a single trait

polygenic inheritance

An additive effect of two or more genes on a single phenotypic character.

Blood type is an example of what?

codominance and multiple alleles

height, skin color, acne are examples of what?

polygenic traits

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape. Shows major chromosomal abnormalities

Autosomes

Any chromosome that is not a sex chromosome

sex chromosomes

X and Y chromosomes.

XX

female

XY

male

Pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family.

pedigree analysis

an inherited trait is analyzed over the course of a few generations in one family

sex-linked traits

Traits controlled by genes located on sex chromosomes.

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

Trisomy

3 copies of a chromosome

Monosomy

missing a chromosome

Trisomy 21

condition in which an individual has three number 21 chromosomes, resulting in Down syndrome

monosomy X

called Turner syndrome, produces X0 females, who are sterile; it is the only known viable monosomy in humans

DNA

deoxyribonucleic acid

Who discovered structure of DNA?

Watson and Crick

Structure of DNA

double helix

sides of DNA

sugar and phosphate

rungs of ladder

nitrogen bases

Nucleotides are composed of

sugar, phosphate, nitrogenous base

DNA nitrogen bases

Adenine, Thymine, Cytosine, Guanine

base pairing

the nearly perfect fit between A-T and G-C nucleotides

Chargaff's Rule

A\=T and C\=G

DNA replication

the process of making a copy of DNA

DNA polymerase

principle enzyme involved in DNA replication

protein synthesis

The creation of a protein from a DNA template.

Transcription

synthesis of a mRNA molecule from a DNA template

Translation

decoding of a mRNA message into a polypeptide chain

amino acids

monomers of proteins

polypeptide chain

A chain of amino acids linked together by peptide bonds.

mRNA (messenger RNA)

The form of RNA which is created as a blueprint from DNA; carries instructions for making a protein

tRNA (transfer RNA)

type of RNA molecule that transfers amino acids to ribosomes during protein synthesis

Codons

The three-base sequence of nucleotides in mRNA

Codons code for what?

amino acids

Anticodons are

complementary to codons; tRNA

Mutations

changes in the genetic material

Mutagens

A chemical or physical agent that interacts with DNA and causes a mutation.

point mutation

Gene mutation involving changes in one or a few nucleotides.

frameshift mutation

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

chromosomal mutation

A change in the structure of a chromosome (e.g., deletion, duplication, inversion, and translocation)

What limits cell size?

surface area to volume ratio

cell division

Process by which a cell divides into two new daughter cells

chromosome structure

2 sister chromatids attached by a centromere; identical DNA

cell cycle

series of events that cells go through as they grow and divide

G1 phase

stage of interphase in which cell grows and performs its normal functions

S phase of interphase

DNA replication

G2

Final preparation phase. Cell checks for DNA errors and begins to form centrioles (Prepares for Mitosis)

Interphase

Cell grows, performs its normal functions, and prepares for division; consists of G1, S, and G2 phases

M phase

mitosis

Mitosis

division of the nucleus

Cytokinesis

division of the cytoplasm to form two separate daughter cells

Prophase

Chromosomes become visible, nuclear envelope dissolves, spindle forms

Metaphase

Chromosomes line up in the middle of the cell

Anaphase

Phase of mitosis in which the chromosomes separate and move to opposite ends of the cell

Centrioles

Cell organelle that aids in cell division in animal cells only

Telophase

phase of mitosis in which the distinct individual chromosomes begin to spread out into a tangle of chromatin

Mitosis vs. Meiosis

Mitosis: one division forming 2 identical cells (clones); Meiosis: two divisions forming 4 genetically different cells

Plant Cell Cytokinesis

cell plate forms

Cancer

disorder in which some of the body's cells lose the ability to control growth

tumor

mass of rapidly dividing cells that can damage surrounding tissue

Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Haploid

having a single set of unpaired chromosomes

Diploid

containing two complete sets of chromosomes, one from each parent.

diploid in humans

46 chromosomes

haploid in humans

23 chromosomes

homologous chromosomes

Pair of chromosomes that are the same size, same appearance and same genes.

crossing over

exchange of genetic material between homologous chromosomes during prophase I of meiosis

phases of meiosis in order

Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II

The purpose of meiosis is to make

gametes that are haploid

Charles Darwin

English natural scientist who formulated a theory of evolution by natural selection (1809-1882)

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

Evidence for evolution

can be found in fossil records, geographical distribution, homologous structures, similarities in early development

Galapagos Islands

Chain of islands near South America where Darwin developed his theory of natural selection by studying the unique life there.

Galapagos Finches

during drought, directional selection favored birds with large beaks

gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time

allele frequency

Number of times that an allele occurs in a gene pool compared with the number of alleles in that pool for the same gene

Types of Natural Selection

directional, stabilizing, disruptive

directional selection

occurs when natural selection favors one of the extreme variations of a trait

stabilizing selection

form of natural selection in which individuals near the center of a distribution curve have higher fitness than individuals at either end of the curve

disruptive selection

favors individuals at both extremes of the phenotypic range

What are the sources of genetic variation?

mutation, genetic recombination during sexual reproduction, and lateral gene transfer

genetic drift

A change in the gene pool of a population due to chance

bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population