Gr 11 Bio Quiz 3 - Genetics

Friedrich Meischer

Discovered a chemical substance called nuclein.

Phoebus Levene

Determined that DNA has 3 main components called adenine, guanine, cytosine, and thymine to make up the basic building blocks called nucleotide. (First 2 purines, last 2 pyrimidines)

Joachim Hammerling

Determined that the nucleus contained genetic material.

Maurice Wilkins

Worked with Rosalind Franklin to take the most important image ever taken of DNA called Photo-51. He ended up winning a Nobel Prize alongside James Watson and Francis Crick.

Rosalind Franklin

Took the most important image ever taken of DNA called Photo-51 and made the 1st model of DNA but died before receiving proper recognition.

James Watson and Francis Crick

Won the Nobel Prize in 1953 for their model of DNA.

Alfred Hershey and Martha Chase

Determined that it was DNA, not protein, that was the transforming principle.

Why is 1953 a significant date?

It is the year in which James Watson, Francis Crick, and Maurice Wilkins won the Nobel Prize for their model of the DNA.

Describe the structure of DNA

Built of 2 strands made up of alternating phosphate groups and pentose sugars. Attached to this backbone are nitrogenous bases: A, T, C, and G. DNA is a double helix structure.

Which nitrogenous bases are pyrimidines?

Cytosine and Thymine

Which nitrogenous bases are purines?

Adenine and Guanine

Describe transcription (What happens? Where does it take place?)

The strands of DNA separates and a complementary RNA strand is made from the DNA template. The DNA then reconnects and the mRNA (messenger RNA) leaves the nucleus to find a ribosome for translation.

Describe translation (What happens? Where does it take place?)

Using the Universal Genetic Code the mRNA is decoded in codons inside the ribosome to form amino acids which are attached by peptide bonds until a stop codon is reached to form a final protein.

What is a codon? What is the start codon? What do the stop codons do?

A group of 3 mRNA nitrogenous bases. The start codon is AUG and it forms the amino acid “Methionine”. Stop codons ends the formation of any more amino acids and promotes the ribosome to release the new protein to fold into its final shape.

What is a mutation? Why are DNA mutations important?

Mutation is when genes are misspelled during translation or transcription. Mutations can cause DNA variation which can help speed up evolution by making the organism new traits which may help it adapt. Mutations can also cause extremely harmful diseases or disorders.

Distinguish between a gene and a genome.

• Gene: an individual DNA segment that codes for only one type of protein.

• Genome: a complete set of an organism’s genetic material including genes and non-coding DNA.

What is the difference between whole genome sequencing and genotyping? Which one is more reliable?

Whole genome sequencing has the entirety of your base pairs read and decoded whereas genotyping only looks at certain snippets of your genome. Whole genome sequencing is more reliable as it looks at all of your base pairs giving a complete analysis whereas genotyping and sometimes give wrong information depending on which parts of your genes is being looked at.

What are actionable genes? Provide an example.

Genetic variants or mutations that, when identified, give healthcare providers clear, evidence-based steps to manage, treat, or prevent a related medical condition. For example: BRCA1.

Plasmid

Rings of DNA that have the ability to enter and exit a bacterial cell.

What is recombinant DNA?

An artificially created DNA molecule formed by joining genetic material from two or more different sources or species that would not normally be found together.

Describe the process of recombinant DNA

To deliver a gene from one organism to another the plasmid and desired DNA are both “cut” by the same restriction enzyme.The DNA is then injected into the plasmid. This plasmid is then exposed to a cell culture to enter bacteria. That bacteria culture is then exposed to the organism allowing the plasmid to enter the cells and introduce the new gene into the genome causing the organism to gain new genes from another organism.

What are some applications of recombinant DNA technology? (hint: think Bt corn)

Scientists take a gene from the soil bacterium Bacillus thuringiensis and insert it into a plant's genome. The crop then produces a natural pesticide which cuts down on production costs and the harmful chemical pesticides.

What are some applications of recombinant DNA technology? (hint: think spider silk goat)

Scientists noticed that spider silk has many beneficial proteins so they injected the spider silk DNA into a goat’s genome so whenever it produces milk it has that added spider silk protein benefit.

What is the goal of gene therapy?

An experimental technique that tries to overcome the negative effects of a defective genes by adding, modifying, or repairing the defective gene.

What are some of the obstacles to gene therapy?

1. The placement of the new gene cannot be fully controlled.

2. If a virus is used as a vector it could trigger an immune response.

3. If a disorder stems from a mutation caused by multiple genes it can be difficult to target.

4. It can be difficult to keep the gene active enough to express it into the gene sequence.

What is mitosis and why is it important?

It is a form of cell division in which a parent cell produces 2 genetically identical daughter cell. It is important for growth, repair, and reproduction.

Describe the steps of mitosis.

• Prophase: The nuclear membrane disappears, chromosomes condense, and spindle fibers begin to form.

• Metaphase: The chromosomes attaches to the spindle fibers and line up the equator.

• Anaphase: The centromere splits and the chromosomes are pulled in opposite directions.

• Telophase: The nuclear membrane reforms into 2 nuclei and each nuclei has the same number of chromosomes as the original cell.

• Cytokinesis: The cytoplasm divides and a cleavage furrow forms (or cell plate if its a plant cell) and it forms 2 new cells. These cells are genetically identical to the parent cell.

What is interphase and why is it important?

It is the longest phase of the cell cycle. During this time the cell grows (G1), duplicates its DNA (S), and grows once more (G2). This phase is important as it prepares the cell for cellular division.

Identify the 3 stages of interphase.

1. G1: The cell grows while continuing to perform its normal tasks.

2. S: The cell duplicates its DNA

3. G2: The cell continues to grow and makes the final preparations for cell division.

How does cytokinesis differ between plant and animal cells?

In animal cells, a cleavage furrow forms and the 2 cells pinches away whereas in plant cells a cell plate forms between the 2 cells and they become their own individual cells.

What is meiosis and why is it important?

It is a type of cell division that occurs only in the ovaries or testes and results in gametes (haploid sex cells). This process is necessary so the number of chromosomes does not double during fertilization.

What does it mean to be haploid vs. diploid?

• Haploid: Contains half the number of chromosomes (one of each homologous pair) (all gametes) (represented by n).

• Diploid: Contains the total number of chromosomes (forms homologous pairs) (all somatic cells) (represented by 2n).

What are homologous chromosomes?

Pairs of similar chromosomes each pair has one chromosome from your mom and your dad. Contains genes for the same traits.

What is a tetrad?

Pairs of homologous chromosomes (4 chromatids).

Describe the steps of meiosis one

Interphase: the cell prepares by growing and duplicating the chromosomes

1. Prophase 1: Tetrads form and the chromatids cross over and exchange segments (one cause of genetic variation)

2. Metaphase 1: Tetrads line up along the equator and form a double-file line (attaches to the centrioles by spindle fibers that are attached to the centromeres)

3. Anaphase 1: The homologous pairs are pulled to opposite ends with each half having an haploid number. Each chromosome is still double stranded.

4. Telophase/Cytokinesis 1: Cytoplasmic division occurs and each daughter cell is haploid and has chromosomes still in their replicated forms.

Describe the steps of meiosis two

1. Prophase 2: New spindle fibers begin to form and sister chromatids begin to move.

2. Metaphase 2: Sister chromatids line up along the equator and form a single filed line

3. Anaphase 2: The centromere splits and the sister chromatids are pulled apart.

4. Telophase/Cytokinesis 2: The single stranded chromosomes are surrounded by a new nuclear membrane and the cytoplasm divides to form 4 haploid daughter cells.

Describe the two processes, occurring in meiosis, that help create genetic variation in gametes.

1. Crossing over: A physical exchange of genetic material between homologous pairs.

2. Independant assortment: The random and independent orientation of the

Describe the two types of gametogenesis.

1. Spermatogenesis: Process through which the testes produces 4 haploid sperm cells per cycle.

2. Oogenesis: Process through which the ovaries produces 1 haploid egg cell and 3 non-functional polar bodies due to unequal cytoplasmic division which end up degenerating per cycle.

How are the two types of gametogenesis the same? How are they different?

The both produce haploid sex cells through meiosis and requires the other for fertilization. They both take place in different organs, produce different quantities of gametes, and different equalities during cytoplasmic division.

What is nondisjunction?

Nondisjunction is when homologous chromosomes fail to properly move apart in meiosis 1 or sister chromatids don’t separate during meiosis 2. If these gametes are involved during fertilization the resulting embryo tends to have too few or too many chromosomes which usually do not survive or have disorders/disabilities.

Compare trisomy to monosomy.

• Trisomy: Fertilized cell with an extra copy of chromosome.

• Monosomy: Fertilized cell missing a chromosome.

What are some disorders caused by nondisjunction?

1. Down syndrome

2. Turner syndrome

3. Klinefelter syndrom

4. Patau syndrome

5. Edwards syndrome

Down syndrome

Trisomy 21: three copies of chromosome 21

Turner syndrome

Only one x chromosme.

Klinefelter syndrome

2 x and 1 y chromosomes

Patau syndrome

Trisomy 13: three copies of chromosome 13

Edwards syndrome

Trisomy 18: three copies of chromosome 18

What is a karyotype?

A picture of a person’s chromosomes. Karyotypes can be used to determine the sex of an individual and to diagnose some chromosome abnormalities such as nondisjunction disorders and disorders resulting from large portions of chromosomes being deleted or duplicated.

Know how to read a karyotype and use proper notation (47, XY, +21)

• Number of chromosomes: 47

• Sex: male

• Trisomy 21 (down syndrome)