bio exam

What is a gene

segment of DNA that codes for a protein

What is a trait?

specific characteristic of an individual

What is an allele

An alternative version of a gene; one from each parent.

What is a genotype

genetic makeup of a specific set of genes

What is a phenotype?

physical characteristics of an organism

What is a dominant allele?

the allele that is expressed when two different alleles or two dominant alleles are present

What is a recessive allele?

the allele that is expressed only when two copies are present

What is homozygous?

Two of the same alleles

What is heterozygous?

two different alleles

What is a monohybrid cross?

a cross that examines the inheritance of only one specific trait

What is a punnett square?

a grid system for predicting all possible genotypes resulting from a cross

What is the law of dominance?

Mendel's 2nd law of inheritance - one gene usually expresses itself over the other (one gene is dominant over the other)

For a mutation to be passed to offspring, in what type of cell must it occur?

sex cells (gametes)

When does crossing over occur?

prophase I of meiosis 1

how does crossing over contribute to genetic diversity?

Crossing over creates new combinations of genes in the gametes that are not found in either parent, contributing to genetic diversity.

What is incomplete dominance?

a heterozygous phenotype is somewhere between the two homozygous phenotypes (a mixture of the phenotypes)

What is codominance?

both traits are fully and separately expressed

What is a polygenic trait?

trait controlled by two or more genes

What is an epistasis

Can interfere with the expression of other genes

What type of inheritance is blood type?

Codominance- both alleles are expressed and the leads to bloody type

What is different on a pedigree if a trait is autosomal? What if it's sex linked?

Autosomal- any chromosome that is not a sex chromosome; everyone will have is about 50/50 between males and females

Sex linked- genes on the sex chromosome; men will have it more than females

What are three types of abnormalities that can be seen on a karyotype

-an extra chromosome, a missing chromosome, or an extra sex chromosome

What is the shape of DNA

double helix (twisted ladder)

What does the DNa carry instructions for making

proteins

Which scientists discovered the structure of DNA

Watson and Crick

What are the 3 parts of a nucleotide?

sugar, phosphate, nitrogen base

How does DNA differ from RNA?

DNA- thymine, double stranded, deoxyribose

RNA- uracil, single stranded, ribose

What are the base pairing rules for DNA?

A=T and C=G

What are the base pairing rules for RNA

A=U, C=G

What is the function of start and stop codons

The start codon marks the site at which translation into protein sequence begins, and the stop codon marks the site at which translation ends.

What are two types of mutations and how are they different

Point- a mutation in which one nucleotide is substituted for another

Frameshift- involves the insertion or deletion of a nucleotide in the DNA sequence

How is a mutation passed onto offspring

When it occurs in the sex cell

What happens during DNA replication

Enzymes and proteins; enzymes start by unzipping the double helix to separate DNA strands and other proteins hold the stands apart while stands serve as templates. Floating free nucleotides in the nucleus then pair up with the nucleotides of the existing DNA strands

Where is replication DNA found?

nucleus

What happens during transcription

RNA polymerase binds to a specific region on a DNA strand and begins to synthesize on a complementary RNA molecule by matching bases to the DNA template

Where does transcription happen

inside the nucleus

What happens during translation

The process by which mRNA is decoded and produces a protein

Where does translation happen

cytoplasm

What is gradualism?

Slow, steady change over geologic time

What is evolution

the process of change over time

What is a species

A group of similar organisms that can breed and produce fertile offspring.

What is a fossil

the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.

What is variation

The difference in physical traits of an individual form those of other individuals

What is adaptation?

A trait that helps an organism survive and reproduce

What is artificial selection?

the process by which humans change a species by breeding it for certain traits

What is natural selection?

the process whereby organisms better adapted to their environment tend to survive and produce more offspring

What is a gene pool

all the alleles in a population

What is genetic variation

Differences among individuals in the composition of their genes or other DNA segments

What is an extinction

The elimination of species from earth

Why does genetic variation increase the chance that some individuals in a population will survive

Because the ones adapted to the environment will survive and reproduce

How does gene flow affect neighboring populations

The organism that reproduces in the neighboring population is adding a new allele to the gene pool, keeping their gene pools similar

How can reproductive isolation lead to speciation?

When two populations become so different because of isolation, they can no longer mate and diverge into two separate species.

What are the three types of barriers that can lead to reproductive isolation? How do they work?

Behavioral- differences in courtship or mating behaviors

Geographical- physical barriers divide populations

Temporal- timing prevents reproduction between populations

What is Interphase?

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

What is Prophase 1 (crossing over)

Chromosomes become visible; nuclear envelope breaks down; crossing-over occurs.

What is Metaphase 1

Paired homologous chromosomes line up across the center of the cell

What is Anaphase 1

Homologous chromosomes separate

What is Telophase 1

2 daughter cells are formed, each daughter cell contains only one chromosome of the homologous pair.

What is Prophase 2

The duplicated chromosomes and spindle fibers reappear in each new cell.

What is Metaphase 2

Centromeres of chromosomes line up randomly at the equator of each cell.

What is Anaphase 2

sister chromatids separate

What is telophase 2

A nuclear membrane forms around the chromosomes in each of the 4 new cells.

What is a dihybrid cross?

A cross between two individuals, concentrating on two definable traits

What is a Pedigree

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

What is gel electrophoresis

Procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel

What is polymerase chain reaction (PCR)

technique that allows molecular biologists to make many copies of a particular gene

What is the Hardy-Weinberg Principle

principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change (mutations, immigration, genetic drift, natural selection, or sexual selection)

What are vestigial structures

remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species.

What are homologous structures

Structures in different species that are similar because of common ancestry.

What are analogous structures

Body parts that share a common function, but not structure

What is directional selection

Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

What is disruptive selection

form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle

What is stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

What is a cladogram?

Diagram that shows the evolutionary relationships among a group of organisms

What is the order of taxa?

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

What is the Dichtomous Key?

A tool that allows the user to determine the identity of organisms in the natural world such as birds, reptiles, wildflowers, and fish