Genetics Exam 1

Genetics

Study of genes, heredity and genetic variation in living organisms

Model Genetic Organisms

Organisms with characteristics that make them useful for genetic anaysis

Common Characteristics of Model Organisms

Short generation time, production of numerous progeny, the ability to carry out controlled genetic crosses, easy to raise in a lab enviornment, the availability of numerous genetic variations

Viruses

Neither prokaryotic nor eukaryotic, outer protein coat surrounding nucleic acid

Homologous Chromosomes

Eukaryotic chromosomes come in pairs

Gene

A genetic factor that helps determine a trait; DNA that leads to transcription of an RNA.

What is a chromosome?

A structure made of DNA and proteins that contain genetic information

What is a chromatid?

One copy of a chromosome

What are sister chromatids?

Two identical copies of a chromosome that are attached to each other at the centromere.

How many chromosomes are shown in an X-shaped replicated chromosome?

One chromosome, even though it contains two sister chromatids

How many chromosomes are shown in an X-shaped replicated chromosome?

One chromosome, even though it contains two sister chromatids

How many chromatids are in a replicated chromosome?

Two sister chromatids

What is the centromere?

The region where sister chromatids are joined together.

What is the kinetochore?

A protein structure located at the centromere where spindle microtubules attach

Where is the kinetochore lcoated?

At the centromere of the chromosome

What are spindle microtubules

Fubers that attach to kinetochores and help move chromosomes during cell divison

Where do spindle microtubules attach to a chromosome?

To the kinetochore

What are telomeres?

Protective regions located at the ends of chromosomes

What is the function of telomeres?

They protect the ends of chromosomes from damage and loss of DNA

Where are telomeres located?

At both ends of each chromosome/chromatid

What happens do sister chromatids during cell division?

They are seperated and oved toward opposite sides of the cell

After sister chromatids seperate, what is each chromatid considered?

Each becomes its own chromosome

Haploid (N)

Cell that contains 1 copy of each chromosome

Diploid (2N)

Cell that contains 2 copies of every chromosome

Mitosis

Separation of sister chromatids into different cells

Cytokinesis

Division of cytoplasm

Meiosis

The production of haploid gametes

Fertilization

The fusion of haploid gametes

Genetic variation

A consequence of meiosis

Interphase

DNA synthesis and chromosome replication phase (same as mitosis)

Meiosis I

Seperation of homologous chromosomes pairs, and reduction of the chromosome number by half

Meiosis II

Separation of sister chromatids, also known as equational division

Synapsis

Occurs during prophase I, close pairing of homologous chromosome

Tetrad

Closely associated four-sister chromatids of two homologous chromosomes

Crossing over

Exchange of genetic info between non-sister chromatids

Metaphase I

Random alignment of homologous pairs of chromosomes along the metaphase plate

Anapahse I

Seperation of homologs and the random distribution of chromosomes into two cells- a second mechanism of generation genetic variation in the newly formed gametes

Consequences of meiosis

Four cells are produced from each original cell, chromosome number in each new cell is reduced by half. the new cells are haploid. Newly formed cells from meiosis are genetically different from one another and from the parental cell

What are sources of genetic variation?

Crossing over, independant assortment

What is heredity?

The transmission of traits from parents to offspring

what was the old ‘blending’ idea of inheritance?

The belief that traits from the parents blend together in offspring

What evidence contradicted blending inheritance?

Hybrid plants sometimes produced offspring resembling the original parental strains rather than an intermediate

Who is considered the father of modern genetics?

Gregor mendel

Approximately how many plants did Mendel cultivate and test?

About 29,000 plants

When did Mendel publish his genetics work?

1866

When was Mendel’s work rediscovered?

1900

Why did Mendel use pea plants?

They had many varieties, were easy to grow, could produce hybrids, and could self-fertilize or cross-fertilize

How many pea characteristics did Mendel study?

Seven.

What is a gene?

An inherited factor or region of DNA that helps determine a characteristic.

What is an allele?

One of two or more alternative forms of a gene

What is a locus?

The specific location on a chromosome occupied by an allele

What is a genotype?

The set of alleles possesed by an organism.

What is a phenotype?

The observable or expression of a characteristic

What is a homozygote?

An organism possessing two of the same alleles at a locus

What is a heterozygote?

An organism possessing two different alleles at a locus

What is a characterisitc?

An attribute or feature possessed by an organism

what does true-breeding mean?

Individuals are homozygous and consistently produced the same phenotype when self-fertilized.

What is the P generation?

The original parental generation used in a genetic cross

What is the F1 generation?

The offspring of the P generation

What is the F2 generation?

The offspring produced by crossing or self-fertilzing F1 individuals.

What is a monohybrid cross?

A cross between parents differing in one characteristic

What happened when Mendel crossed homozygous round peas with homozygous wrinkled peas?

All F1 seeds were rounded

What does dominant mean?

The allele whose trait is expressed in a heterozygote

What does recessive mean?

The allele whose trait is masked in heterozygote.

What is a gene?

A region of DNA that helps determine a characteristic

What is an allele?

An alternative form/DNA sequence of a gene

What is a locus?

The location of a gene on a chromosome

What is a geneotype?

The alleles an organism possesses

What is a phenotype?

The observable of an expression of a characterisitc

Homozygous means what?

Two different alleles

What is a dominant allele?

An allele expressed in a heterozygote

What is a recessive allele?

An allele masked by the dominant allele in a heterozygote

What is the P generation?

The parental generation

What is the F1 generation?

Offspring of the P generation

What is the F2 generation?

Offspring produced from the F1 generation

What does true breeding mean?

Homozygous for the trait being studied

What is a monohybrid cross?

A cross involving one characterisitc

What is Mendel’s Law of Segregation?

The two alleles for a gene seperate during gamete formation

What is a Punnett square?

A tool used to predict possible offspring genotypes

What is a test cross?

Crossing an individual with a dominant phenotype and unknown genotype with a homozygous recessive individual

What is a dihyrbid cross?

A cross involving two characteristics

What are linked genes?

Genes on the same chromosome htat tend to be inherited together

What are unlinked genes?

Genes on different chrmosomes that can assort independantly

What is independent assortment?

Allele pairs for different genes segregate independently during gamete formation

Probability rule of AND?

Multiply

Probability rule for OR?

Divide

What is conditional probability?

Probability recalculated using additional known information