unit 3 test review - genetics

List the 4 basic functions of cell division.

• Repair, replace, reproduce, and grow cells

Why can cells not grow in size indefinitely?

• Cells are limited in size because of limitations in their surface area to volume ratio, nutrient intake, and internal transport
• As cells grow larger, the essential materials travel within the cell less effectively

Why is accurate cell division required for biological continuity?

• Accurate cell division ensures:
  • New cells receive the correct number of chromosomes
  • Preserving genetic information across generations.

What is chromatin?

• Fibres of SNA in its uncondensed form

How are chromatin and chromosomes related to one another?

• Chromatins condense to form chromosomes during cell division
• Chromosomes are made of tightly coiled chromatin

What is the importance of chromatin replication to successful cell division?

• Ensures new cell receives a complete set of DNA

List and describe the stages of chromatin replication.

• Initiation: Enzymes unwind the DNA at specific origins.
• Elongation: New strands of DNA are synthesized using each original strand as a template.
• Termination: DNA replication stops and the strands are checked for errors.

What is mitotic cell division?

• Occurs in all cells except gametes
• 1 cell division
• 2 final daughter cells produced
• Same number of chromosomes in daughter cell compared to parent cell (diploid 2n = (n = 23))
• No tetrads (synapsis chromosomes)
• No crossing over
• Identical genetics to parent cell
• Repair, growth, reproduction

How much of a cell's life is spent in interphase and mitosis:

• Interphase: 95% of the cell’s life
• Mitosis: 5% of their cell-cycle time (less than 1 hour)

How can each of the following stages of mitosis be recognized?

• Interphase
  • Cell prepares to divide: growth, DNA replication, cell functions
• Early prophase
  • Chromatin begins to condense into visible chromosomes, nucleus present
• Late prophase
  • Nuclear membrane breaks down; spindle fibers being to attach to chromosomes
• Metaphase
  • Chromosomes line up in the middle (equator) of the cell
• Anaphase
  • Sister chromatids are pulled apart to opposite sides of the cell
• Telophase
  • Two new nuclei start to form; chromosomes begin to uncoil; spindle fibers disappear.
• Cytokinesis:
  • Two new daughter cells are produced

What are chromatids and centromeres?

• Chromatids:
  • Fibres of SNA in its uncondensed form
  • Exists during S phase of interphase to allow DNA to replicate
• Centromeres:
  • The region where sister chromatids are joined and where spindle fibers attach during mitosis.

Describe cytokinesis in a plant cell

• A cell plate forms in the center of the cell
• Develops into a new cell wall, dividing the cell into two

How does this differ from animal cell cytokinesis?

• The cell membrane pinches inwards to divide the cell into two
• Called the cleavage furrow

State another difference between plant and animal cell mitosis.

• No cell wall and cell plate in animal cells
• Animal cells have cleavage furrow in telophase rather than a cell plate

What is meiotic cell division?

• Occurs in gamete cells
• Double (2) the cell division (PMAT occurs twice)
  • IPMAT I and PMAT II
• 4 final daughter cells produces
• Half amount of chromosomes as parent cell (haploid n)
• Tetrads form (synapsis chromosomes)
• Crossing over in prophase I
• Genetically different from parent cell
• Genetic diversity (genetic variation)

What is meant by the terms haploid (n) and diploid (2n):

• Haploid
  • Contains half the number of chromosomes (n) as the parent cell (2n)
  • Ex. sperm and egg cells in humans, meiosis
• Diploid
  • Containing pairs of chromosomes
    • All somatic cells are diploid
    • In humans 2n = 46
    • Zygote has 2n (n from female + n from male gametes)

What are homologous chromosomes?

• Pair of chromosomes with the same genes at same location
• NOT identical
  • May carry different versions of the gene/trait (alleles)
• Same: Length, centromere location, banding pattern when stained

How does cytokinesis of meiotic cell division differ in males and females in humans?

• Males = four equal sperm cells
• Female = unequal, haploid one large egg cell (ovum) and 3 smaller polar bodies cells (which degenerate)

Errors in Meiosis

• Two types of errors: Structure and Number
• Structure
  • Deletion: a piece of chromosome is deleted
  • Duplication: Chromosome section appears twice or more times
  • Inversion: Section of chromosome is inverted
  • Translocation: segment of chromosome is attached to a different non-homologous chromosome (it should pair with homologous (same chromosome))
• Number
  • Nondisjunction: when homologous chromosome pairs or sister chromatids do nope separate during meiosis

Why are pea plants an ideal organism for studying inheritance? (give 2 reasons)

• Easy and observable traits (ex. color and seed shape)
• Reproduce quickly (cross pollination or self pollination)

State Mendel's Principle of Dominance.

• When two different alleles are present, the dominant will show/mask to effect the recessive trait

State Mendel's Principle of Segregation.

• Alleles of genes separate during meiosis and each offspring receives one allele from each parent.

What is meant by the term incomplete dominance?

• No allele is completely dominant
• Blending phenotype
• New combination created

What is meant by the term codominance?

• Both traits/alleles are shown/expressed
• Heterozygous organism
  • Ex. black cow x white cow = cow with black and white spots

What is the purpose of a test cross?

• Determines genotypes of an organism showing a dominant trait
• Shows homozygous dominant or heterozygous

What disadvantage can you foresee in performing test crosses?

• Time consuming
• Many offspring to get clear results
• Many results to consider

Distinguish between autosomes and sex chromosomes. How many pairs of each type do humans have?

• 46 total chromosomes in humans
• Autosomes: non sex chromosomes, control most traits, 22 pairs (44 chromosomes)
• Sex chromosomes: determine sex (XX female or XY male), 1 pair (2 chromosomes)

Sex-linked traits examples

• Color Blindness
• Hemophilia (body’s ability to make blood clots)

What is a pedigree? How can a pedigree help to trace genetically inherited traits?

• A diagram of individual’s ancestors
• Used in human genetics to analyze Mendelian inheritance of a certain trait
• Used to track the inheritance of a gene

About Blood / Blood Types

• Types: A, B, AB, O
  • IAIA / IAi, IBIB / IBi, IAIB, ii
• Antigens
  • Substances (usually proteins)
  • Tiny markers on the surface of cells
  • Help determine blood type
  • Immune system uses antigens to recognize which cells belong in the body and which doesn’t
• Antibodies
  • Tiny proteins made by the body to fight off foreign antigens (blood types)
  • Look and attack cells that don’t belong
    • Such as wrong blood types
• Rh blood group (+) or (-)
  • Another kind of antigen on red blood cells
  • Have it = Rh (+)
  • Don’t have it = Rh (-)
• Agglutination
  • When blood cells clump together
    • Blocks blood flow and is dangerous
• Hemolysis
  • When red blood cells break open and release its contents
  • Happens due to bad reactions such as blood clotting
  • Can lead to serious damage like kidney damage

Definitions

• Genetics
• The study of heredity and variation of living organisms
• How genetic information is passed from one generation to the next
• Allele
• A trait/gene inherited from generations / parents
• Dominant allele
• Form of a trait that always appears when an individual has alleles for it
• Expressed in capital letters
• Recessive allele
• Form of a trait that always appears when an individual has 2 alleles for it (ex. aa)
• Phenotype
• Physical appearance/traits of an organism
  • ex . GOP: red x white
• Genotype
• Combination of alleles for any given trait / genetic makeup
  • Ex. GOP: XBXb x XbY
• Gene
• A designated segment of DNA on a chromosome
• Position of a gene on a chromosome is called locus / loci
• Genome
• The complete DNA sequence of an organism
• DNA
• The chemical name for the molecule
• Carries genetic instructions in all living things
• Packaging of DNA with histone proteins for storage to result in a condensed chromosome
• Structure: Have 3 components of nucleotides: Phosphate group, Pentose group, Nitrogenous bases
  • A, G, C, T/U,
  • Adenine (A), Guanine (G), Cytosine (C), Thymine (T) (DNA), Uracil (U) (RNA)
    • Base Pairing: A pairs with T/U (2 hydrogen bonds)
    • Base Pairing: G pairs with C (3 hydrogen bonds)
• Somatic cell
• A plant or animal cell that forms the body of the organism (not reproductive cells)
• Karyotype
• A photograph of sorted and paired homologous chromosomes in a cell
• Can show missing or additional chromosomes in a person
  • Helps determine chromosome errors and disabilities
• Zygote
• Result of a cell from two gametes fusing
• Synapsis
• The alignment of homologous chromosomes
• During prophase I and meiosis I
  • AKA crossing over (segments of DNA exchange with each other)
• Chiasma
• Point of contact or physical link between two non-sister chromatids
• Trisomy
• Gain an extra chromosome
  • Ex. down syndrome
• Monosomy
• Loss of one chromosome (nondisjunction)
  • Most are lethal (dangerous/deadly)
  • Can cause miscarriage
• Genetic Reduction (outcome of meiosis)
  • Produces haploid daughter cells
• Genetic Recombination (outcome of

Domainant Allele

• Form of a trait that always appears when an individual has alleles for it

• Expressed in capital letters

Recessive Allele

• Form of a trait that always appears when an individual has 2 alleles for it (ex. aa)

Sex Linked Traitmitosis

A gene located on the sex chromosomes. Examples include color blindness and hemophilia.

• Males are more common of sex linked traits because they only have one X chromosome (XY), while females have (XX) so the trait would result higher as a recessive trait than dominant

Oogenesis

The production or development of an ovum.

• Producing female gametes (eggs or ova)

Spermatogenesis

The process of producing male gametes (sperm) in males.

Zygote

The fertilized egg formed when a sperm cell merges with an ovum. It marks the beginning of a new organism's development.

Fertilization

The biological process in which a sperm cell unites with an ovum, leading to the formation of a zygote.

Gene

The basic unit of heredity passed from parent to child. Carries instructions for building proteins or functional RNA molecules