Genetics 2038 test 1 ch 1-4 Flashcards Preview

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Flashcards in Genetics 2038 test 1 ch 1-4 Deck (83):
1

Genetics is important

it influences our lives, contribute to our personality, and are fundamental to who and what we are. It affects disease susceptibility. It is important in agriculture. It is important in medicine.

2

What is the genome

complete set of genetic instructions; EITHER DNA or RNA; copies made during replication process.

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3 General Divisions of Genetics (can overlap):

Transmission Genetics, Molecular Genetics, and Population Genetics:

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Transmission genetics:

look at how genes transmit to offspring

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Molecular genetics:

look at structure of genes and how they function

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Population genetics:

look at how genes change within a population of organisms

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What 5 qualities do Model organisms studied in genetics possess?

1. Rapid, numerous production of offspring
2. Can be easily manipulated during mating
3. Able to grow and reproduce in a lab setting
4. Many known genetic variants exist and are obtainable
5. Much knowledge has been accumulated about their genetic systems

8

name the 7 Model organisms that are frequently studied in genetics

D. melanogaster, E. coli, C. elegans, A. thaliana, M. musculus, S. cerevisiae, D. rerio

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Central Dogma:

DNA to RNA to Protein – using the processes of replication, transcription, and translation

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3 Chromosomes qualities of Prokaryotes

do not have true chromosomes; DNA is not surrounded by nuclear membrane, nor is it complexed with histone proteins.

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3 Chromosomes qualities of eukayotes

do have true chromosomes, where DNA is surrounded by a nuclear membrane, and the DNA wraps around histone proteins to form chromatin (the material which makes up the chromosomes).

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Viruses are NEITHER - name 2 qualities

their genetic structure is a nucleic acid surrounded by a protein coat (either DNA or RNA, protein coat around these)

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3 facts about Replication in Prokaryotes

“chromosome” is circular DNA (no histones); replication is simple division, with a high rate of production of new copies of DNA

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3 facts about Replication in Eukaryotes:

1. Chromosomes have a particular structure;
2. replicated during a process known as the Cell Cycle. This cycle allows for copies of DNA to be produced AND for new cells to be made.

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BOTH Prokayotes and Eukayotes have

ORIGINS of replication, where the production of new DNA begins. There can be MULTIPLE origins of replication with regard to one DNA molecule.

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The Cell Cycle 2 primary Phases:

Interphase and M phase

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Interphases consist of which steps

G1, G1/s checkpoint, S, S/G2 checkpoint G2 –

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G1 –

growth (cells can enter G “zero” – a non-dividing phase)

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S

DNA duplication

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G2

growth and preparation for M phase

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Checkpoints:

determine whether cell can continue in the Cell Cycle

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M phase (Mitosis or Meiosis) steps

Prophase, metaphase, anaphase and telophase

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different between mitosis and meiosis

during these steps, the chromosomes separate their sister chromatids.

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Cytokinesis is the

separation of the cytoplasm of the cell into new cells.

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G1/S – checkpoint

if proteins required for cell division are not produced, cell will not move on

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S/G2– checkpoint

if DNA is completely replicated and damage is repaired, cell will continue

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Sexual Reproduction meiosis

Meiosis produces haploid gametes, which then fuse (fertilization); genetic variation exists due to the processes of meiosis and fertilization

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Sexual Reproduction: Plants and animals differ in how they produce these gametes

many plants have multiple haploid cells rather than just a single, gametic cell (egg and sperm).

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Proteins are the key to

allowing the Cell Cycle to operate successfully!

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Cohesin

holds chromatids together; its breakdown allows sister chromatids to separate from each other (and homologous pairs of chromosomes to do so as well);

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a second protein, shugoshin,

prevents the degradation of some cohesin during Anaphase I so that homologs separate, but not the chromatids.

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Monohybrid cross

cross between two parents that differ in a single characteristic

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Law of Segregation:

two alleles for a trait segregate (separate) and one allele goes into each gamete (during cell reproduction

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Independent Assortment:

Alleles separate from each other, and independently of how OTHER pairs of alleles separate

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Mendel studied the

Principles of Heredity

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Prophase I

Chromosomes condense, homologous chromosomes synapse, crossing over takes place, the nuclear envelope breaks down, and the mitotic spindle forms.

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Metaphase I

Homologous pairs of chromosomes line up on the metaphase plate.

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Anaphase I

The two chromosomes (each with two chromatids) of a homologous pair separate and move toward opposite poles.

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Telophase I

Chromosomes arrive at the spindle poles.

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Cytokinesis

The cytoplasm divides to produce two cells, each having half the original number of chromosomes.

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Interkinesis

In some types of cells, the spindle breaks down, chromosomes relax, and a nuclear envelope re-forms, but no DNA synthesis takes place.

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Prophase II*

Chromosomes condense, the spindle forms, and the nuclear envelope disintegrates.
Only in cells in which the spindle has broken down, chromosomes have relaxed, and the nuclear envelope has re-formed in telophase I. Other types of cells proceed directly to metaphase II after cytokinesis.

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Metaphase II

Individual chromosomes line up on the metaphase plate.

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Anaphase II

Sister chromatids separate and move as individual chromosomes toward the spindle poles.

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Cytokinesis

The cytoplasm divides.

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Gene

An inherited factor (encoded in the DNA) that helps determine a characteristic

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Allele

One of two or more alternative forms of a gene

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Locus

Specific place on a chromosome occupied by an allele

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Genotype

Set of alleles possessed by an individual organism

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Heterozygote

An individual organism possessing two different alleles at a locus

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Homozygote

An individual organism possessing two of the same alleles at a locus

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Phenotype or trait

The appearance or manifestation of a characteristic

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Characteristic or character

An attribute or feature possessed by an organism

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Independent Assortment:

Alleles separate from each other, and independently of how OTHER pairs of alleles separate

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We can use probability to predict

the outcomes of a genetic cross:

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Multiplication Rule

Probability of obtaining a particular outcome FIRST, and THEN a second particular outcome, is each outcome’s probability MULTIPLIED by the other.

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Addition Rule:

The probability of obtaining a particular outcome OR a second outcome is each probability ADDED together.

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If the probability of being blood type A is 1/8, and that of blood type O is ½,

then the probability of EITHER is 5/8.

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If the probability of obtaining short tail is ¼; probability of getting long legs is ¼; probability of getting BOTH traits is

BOTH traits is ¼ x ¼ = 1/16. multiplication rule

60

Chi-Square Test for

“Goodness of Fit”: If observed ratios of offspring deviate from what you expect (based on probability), then you can indicate how probable this difference between observed and expected is DUE TO CHANCE

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Sex determination is due to

presence or absence of particular sex chromosomes in most organisms:

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Sex determination In humans and other mammals

In humans and other mammals, the X and Y chromosome help determine sex (XX is female, XY is male); other examples are XX-female, XO-male

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Sex determination in other organisms is due to the

presence or absence of genes ONLY (GENIC sex determination): Some plants, some fungi, some protozoans, and some fish

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Sex determination other examples are XX-female, XO-male- name 3-4 insects

grasshoppers and other insects such as bees, wasps, ants

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ZZ-male, ZW-female are for which species (3-4)

birds, snakes, butterflies, some amphibians, some fishes

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Sex determination CAN be changed in some organisms by

ENVIRONMENTAL factors

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environmental factors in limpets control sex by

lowest position in the stack is female, others male (switch to female)

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environmental factors in limpets control sex by

: lower temperature produces more males, higher produces more females

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Sex determination can be a BALANCE of

sex chromosomes and AUTOSOMES (Genic BALANCE system):

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Sex determination in Drosophila melanogaster

Ratio of X chromosome number to the number of HAPLOID sets of autosomes – this is written as X:A –

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Sex determination in Drosophila melanogaster in females

Females have ratio of 1.0 or GREATER

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Sex determination in Drosophila melanogaster in males

Males have ratio of 0.5 or LESSER

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Sex determination in Drosophila melanogaster intersex

Intersex have ratio between 0.5 and 1.0

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in humans Maleness is determined by the

SRY gene on the Y chromosome

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Syndromes are based on the

presence/absence of that gene

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Turner syndrome

XO

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Klinefelter syndrome

XXY or XXXY

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Poly X female

XXX or XXXX

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Male phenotype produced as long as the

SRY gene is operating correctly

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Androgen-insensitivity syndrome

defective androgen receptor, NOT defect in SRY gene

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Sex-linked traits

determined by genes on the sex chromosomes

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X-linked traits (on the X chromosome) can be

altered in their effects due to chromosomal inactivation – Barr

83

Barr bodies in female cells, are responsible for

tortoiseshell coat color in cats. inactive X gene is not expressed and only the hair color linked to the active X chromosome is expressed.