Genetics - unit 4.1 - 4.3

List the four nitrogenous bases found in DNA

• A →Adenine

• C →Cytosine

• T →thymine

• G →guanine

Explain why DNA’s structure is called the double helix

• because it has two strands of many nucleotides wrapped around each other

If the six bases on one strand of a DNA double helix are AGTCGG what are the six bases on the complementary section of the other strand?

• TCAGCC

What is the main difference between a histone and a nucleosome?

• Histone are the proteins that DNA wraps itself around

• Nucleosomes are histones + DNA wraps

What is the difference between a nitrogenous base and a nucleotide?

• Nitrogenous base is a component of the nucleotide that is found in the middle of DNA strands while the outside of the DNA is the phosphate groups

Describe the components of a DNA molecule

• Made of nucleotides connected together in two strands that are wrapped around each other to form a double helix, which comprise of:

  • Phosphate group

  • Deoxyribose sugar (made of 5-carbon sugars)

  • Nitrogenous base (A, C, G, T)

What is the difference between nitrogenous bases that are purines and nitrogenous bases that are pyrimidines? Which nitrogenous bases are pyrimidines or purines?

• Purines →double-ringed structures

  • Adenine

  • Guanine

• Pyrimidines →single-ringed structures

  • Thymine

  • Cytosine

Based on the diagrams which nitrogenous bases are purines and pyrimidines

• Purines:

  • Adenine

  • Guanine

• Pyrimidines:

  • Thymine

  • Cytosine

What is an organism’s genome

• The complete genetic makeup of an organism (everything inside nucleus)

What is chromatin in DNA organization?

• chromatin are a bunch of nucleosomes organised together to form long fibres

What are the complementary bonds of the nitrogenous bases, A, C, T, G

• A →T

• C → G

What are the functions of nitrogenous bases

• holds information that codes for the amino acid sequences into proteins

List the following phases of the cell cycle in sequence and briefly describe what occurs in each:

M phase, S phase, G2 phase, G1 phase

• G1 phase

  • Rapid growth for the cell

  • Production of proteins and organelles

• Synthesis phase

  • Synthesis of a duplicate copy of the cell’s DNA

  • Key proteins associated with chromosomes (like the centromere) are produced during this phase

• G2 phase

  • Shortest phase

  • Production of organelles and structures needed SPECIFICALLY for cell division

• Mitosis phase

  • cell division occurs to produce two identical daughter cells

Why is it necessary for a cell to replicate its DNA prior to cell division?

• because if it doesn’t, the daughter cells won’t be identical and just have pieces of the original DNA

What are telomeres? And in what way do telomeres protect genetic information?

• Telomeres are high repetitive sequences of nucleotides in DNA strands that do not code for anything

• They protect genetic material because after each cell division, a part of your genetic material gets shortened and so telomeres prevent important information from getting shortened

How many chromosomes does a human body cell contain in each of the following periods:

a) G1 phase

b) Prophase

c) just before mitosis

c) After Cytokinesis

a) 46 singular

b) 46 duplicated

c) 92 singular

d) 46 singular

Interphase is sometimes describes as a “resting phase”. Why is this description inaccurate?

• Because during interphase the cell performs its daily functions and prepares for cell division

Suggest what would happen to a single-celled organism if it were to go through many rounds of mitosis but did not go through cytokinesis

• A bunch of nucleuses would be in one cell with a lot of chromosomes

a) Which type or types of cells listed in the table would undergo mitosis? Explain.

b) Red blood cells do not contain nuclei. Explain how this fact relates to red blood cells’ inability to divide

a) some nerve cells and all smooth muscle cells

b) Red blood cells don’t have nuclei to maximize their holding of oxygen and without a nucleus there is no DNA, and without DNA u can't duplicate a cell

Draw and label the following structures:

a) an individual chromosome

b) sister chromatid

List the 4 stages of mitosis and briefly describe them

• Prophase

  • chromatin DNA condenses to form chromosomes

  • Nucleus breaks down

  • mitotic spindle starts to form

• Metaphase

  • Mitotic spindle is fully formed

  • mitotic spindle moves the chromosomes to the middle of the nucleus and lines them up along the metaphase plate

• Anaphase

  • Mitotic spindle pulls sister chromatids apart from the centromere to opposite sides of the cell

• Telophase

  • singular chromosomes wind back to chromatin

  • mitotic spindle breaks down

  • nucleus begins reforming

• Cytokinesis (not really in mitosis but in M phase)

  • Happens alongside telophase

  • Cell membrane pinches in to create a cleavage furrow and eventually splits one cell into two identical cells

What is the metaphase plate

• the imaginary middle line the chromosomes line up along in metaphase

What is the function of the mitotic spindle

• to move the chromosomes around the cell (align them then separate the sister chromatids)

Human nerve cells rarely undergo mitosis. On the basis of this info, why do u think complete recovery from a nervous system injury is rare.

• Because when an injury happens, cells can’t duplicate themselves to repair the damage

What is the difference between cytokinesis in a plant and cytokinesis in animals/humans

• Animals:

  • Pinches through middle easily to create a cleavage furrow and then leads to creating two identical daughter cells

• Plants:

  • Plant cells have rigid walls, so a specialized structure called a cell plate forms in the middle and separates the two daughter cells and eventually forms the edges of the walls for each daughter cell and separates them

What is apoptosis in cells

• self destruction

• When a cell gets too old, it no longer goes through the cell cycle and undergoes cell death : apoptosis

Identify the processes of meiosis and order them (includes interphase)

1. Homologous chromosomes line up in the center of the cell

2. Spindle fibers pull homologous pairs to the ends of the cell

3. 4 haploid (N) daughter cells form

4. Cells undergo a round of DNA replication

5. Sister chromatids separate from each other

6. 2 haploid (N) daughter cells form

7. Spindle fibres attach to the homologous chromosome pairs

8. Individual chromatids move to each end of the cell

9. crossing-over (if any) occurs

1. Metaphase I

2. Anaphase I

3. Telophase II / Cytokinesis

4. Interphase

5. Anaphase II

6. Telophase I / Cytokinesis

7. Prophase I

8. Anaphase II

9. Prophase I

Compare the number and types of cells that result from meiosis vs mitosis

• Meiosis

  • Results in 4 gametes

• Mitosis

  • Results in 2 somatic cells

How do the genetic contents of the cells resulting from mitosis and meiosis differ?

• Mitosis

  • Diploid

  • Identical

• Meiosis

  • Haploid

  • Genetically different

Comparing and contrasting: Describe a similarity and a difference between meiosis I and meiosis II

• Similarity:

  • Both result in genetically different daughter cells

• Differences:

  • Sister chromatids are still attaches in meiosis I while not in meiosis II

  • Meiosis I produces 2 daughter cells while meiosis II produces 4 daughter cells

If a diploid cell containing 28 chromosomes undergoes meiosis, how many chromosomes will each daughter have

• 2n = 28

• n = 14

• Each daughter will have 14 chromosomes

How are mitosis and meiosis similar and different?

• Similar:

  • Both produce daughter cells

  • Involves same steps of prophase, metaphase, anaphase, telophase

  • DNA copied in synthesis

• Differences:

  • Mitosis produces 2 identical daughter cells (2 somatic cells)

  • Meiosis produces 4 genetically different daughter cells ( 4 gametes)

Read each statement, and then on the line write down the phase of mitosis or meiosis that the action occurs. IF the action occurs in both, write both

1. Homologous chromosome line up in the center of the cell

2. The individual chromosomes move apart

3. Spindle fibres pull homologous pairs to ends of the cell

4. 4 haploid (n) daughter cells form

5. cells undergo a round of DNA replication

6. The chromosomes line up across the middle of the cell

7. Chromosomes become visible

8. Sister chromatids separate from each other

9. 2 haploid (n) daughter cells form

10. Sister chromatids separate into individual chromosomes

11. Nuclear envelope re-forms

12. Spindle fibers attach to the homologous chromosomes pairs

13. Individual chromatids move to each end of the cell

14. The nucleus disappears and the nuclear envelope breaks down

15. Each chromosome is connected to a spindle fiber

16. crossing over (if any) occurs

1. Metaphase I

2. Anaphase, anaphase II

3. Anaphase I

4. Telophase II / Cytokinesis

5. Interphase

6. Metaphase, Metaphase II

7. Prophase, Prophase I

8. Anaphase, Anaphase II

9. Telophase I / Cytokinesis

10. Anaphase, Anaphase II

11. Telophase, Telophase I + II

12. Metaphase I

13. Anaphase, Anaphase II

14. Prophase, Prophase I + II

15. Metaphase, Metaphase II

16. Prophase I

1. Anaphase I

2. Anaphase II

3. Prophase I

4. Metaphase I

5. Metaphase II

6. Telophase I / Cytokinesis

7. After telophase I and cytokinesis

8. After telophase II and cytokinesis

During which phase of the meiotic cell cycle does DNA replication occur?

a. interphase

b. prophase

c. metaphase

d. anaphase

e. telophase

a.

When does crossover take place in meiosis

a. interphase

b. prophase

c. metaphase

d. anaphase

e. telophase

b.

During which phase of meiosis does the nuclear membrane reform around chromosomes?

a. interphase

b. prophase I

c. metaphase II

d. anaphase I

e. telophase II

e.

A human cell containing 22 autosomes and a Y chromosome is

a. a somatic cell of a male

b. a zygote

c. a somatic cell of a female

d. a sperm cell

e. an ovum

d.

Homologous chromosomes move towards opoosite poles of a dividing cell during…

a. mitosis

b. meiosis I

c. meiosis II

d. fertilization

e. binary fission

b.

Meiosis II is similar to mitosis in that…

a. homologous chromosomes synapse

b. DNA replicates before the division

c. The daughter cells are diploid

d. sister chromatids separate during anaphase

e. the chromosomes number is reduced

d.

Metaphase of meiosis I and meiosis II differ in that…

a. chromosomes line up at the equator

b. homologous line up in meiosis I and duplicated chromosomes line up in meiosis II

c. Sister chromatids line up in meiosis I and chromosomes line up in meiosis II

d. there are the same number of chromosomes

b.

Asexually reproducing organisms produce offspring that are genetically identical to each other and to the parents. What type of cell division are the offspring a product off?

a. mitosis

b. meiosis

c. binary fission

d. fertilization

a.

At which stage of meiosis do chromatids seperate and become daughter chromosomes?

a. metaphase I

b. anaphase I

c. metaphase II

d. anaphase II

e. telophase II

d.

The process in which haploid gametes are formed in diploid organisms is called:

a. cytokinesis

b. interphase

c. meiosis

d. mitosis

e. nuclear division

c.

Which of the following correctly ranks nucleic acid structures in order of size, from smallest to largest

a. Chromosome, nucleotide, gene, codon

b. nucleotide, codon, gene, chromosome

c. chromosome, gene, codon, nucleotide

d. codon, nucleotide, chromosome, gene

b.

A human cell containing 44 autosomes and two x chromosomes is

a. a somatic cell of a male

b. a zygote

c. a somatic cell of a female

d. a sperm cell

e. an ovum

c.

Independent assortment is one of the factors that contributes to genetic diversity. Independent assortment is associated with which stage of meiosis

a. anaphase I

b. prophase I

c. metaphase I

d. anaphase II

e. metaphase II

c.

The fertilized egg (zygote) of a human contains how many chromosomes?

a. 1

b. 22

c. 46

d. 23

e. 48

c.

Which cells of the human body are made through the process of meiosis

a. gametes

b. somatic cells

c. all cells of the body

d. X and Y chromosomes

e. autosomes

a.

A _______________ is the complete set of chromosomes of an organism, arranged, and displayed in pairs and ordered by size (select Best answer)

a. genome

b. karyotype

c. nucleus

d. heredity

e. gene

b.

Which 2 cells would be more genetically similar to each other?

a. two gametes produced by the same person

b. two somatic cells produced by the same person

c. two eggs produced by the same woman

d. two sperm produced by the same man

b.

If a diploid organisms has a genome consisting of 22 chromosomes, its gametes will have ____ chromosomes

a. 44

b. 11

c. 22

d. 88

e. 19

b.

When does DNA replication occur during meiosis

a. interphase I

b. prophase I

c. interphase II

d. prophase II

e. interphase I and II

a.

go to diagram in last pages of meiosis package and practice that

What is chiasma

• the region of crossing over and connection and exchange of the homologous pairs chromosomes

What is a chromosomal mutation? What are the different types?

• When there is the correct number of chromosomes but changes in the gene sequences

• Inversion

• Duplication

• Deletion

• Translocation

What is a karyotype?

• display of all the condensed chromosomes arranged in pairs

a) what is chorionic villus sampling (CVS)?

b) what are the benefits of prenatal genetic testing using CVS?

c) what are some risks associated with this procedure?

a) Taking tissue from the chorionic villi tissues in the area surrounding the fetus and having it tested

b) finding out if your baby has any genetic disorders ahead of time

c) Maternal bleeding, miscarriage, premature birth

What is prader-willi syndrome? What are some characteristics of prader-willi syndrome?

• Prader-willi syndrome happens when there is a deletion in chromosome 15

• characteristics include:

  • reduced muscle tone

  • obesity

  • short stature

  • reduced hormone production

  • extreme flexibility

  • developmental delays

  • learning disabilities

Give an example of a genetic condition that can result from errors in meiosis

• down syndrome

• patau syndrome

• Edwards syndrome

• Klinefelter syndrome

what do the following show

a) inversion

b) translocation

What is the karyotype of an individual with Klinefelter syndrome?

• has XXY

Suppose an animal has a diploid number of 6 chromosomes (2n = 6). If a trisomy were to occur in one of the animals gametes, how many chromosomes would that gamete contain?

• 4

Suppose an individual has the karyotype XXX. Explain what might have occurred in their parent’s gamete that resultured in this karyotype

• meiosis during egg cell of mom went through nondisjunction, meaning one of the chromosomes did not separate during anaphase 1 or 2

Explain why individuals might have problems from inversion

• because when a chromosome does inversion and then does crossover with another chromosome, it can cause a gene to be duplicated or deleted (draw it out)

draw out non-disjunction for anaphase I and anaphase II in cells during meiosis

what causes down syndrome and what are the characteristics?

• trisomy 21

• characteristic facial features

• below average height and poor muscle tone

• mild to moderate intellectual disability

what causes patau syndrome and what are some characteristics

• trisomy 13

• severe intellectual disability

• heart defects

• poorly developed eyes

• cleft lip

• extra fingers/toes

• weak muscle tone

• brain or spinal cord abnormalities

what causes Edwards syndrome and what are some syndromes

• trisomy 18

• severe intellectual disability

• low birth weight

• small and abnormally shaped head

• small jaw and mouth

• clenched fists

what causes klinefelter syndrome and what are some characteristics

• xxy

• small testes do not produce enough testosterone

  • can fix with injection testoerone

• when puberty hits they get boobs

• infertile

• reduced facial and body hair

What causes translocation down syndrome

• translocation between chromosomes 14 and 21

what causes cri du chat syndrome and what are some characteristics

• deletion of portion of chromosome 5

• abnormal larynx and epiglottis that produces a distinct sounding cry

• poor muscle tone

• small head with distinct facial features

• moderate intellectual disability

what causes prader-willi syndrome and what are some symptoms

• deletion of chromosome 15

• developmental delays

• learning disability

• obesity

• short

• decreased muscle tone

• reduced hormone production

• very flexible

what causes fragile x syndrome and what are some characteristics

• usually there’s 55 CGG sequences in one of the genes but here there’s 200 CGG

• range of learning disorders

• behavioural challenges

• speech and language problems

• distinctive facial features

  • large ears

  • long fae

  • prominent jaw

What are the 4 different genetic testing Post birth

1. karyotype analysis

2. carrier testing

3. presymptomatic testing

4. diagnostic genetic testing

what is carrier testing

• when u screen fror specific gene sequences

• can determine if an individual carries a copy of a mutation that his or her children could inherit

what is presymptomatic testing

• done if u have family history of a genetic condition

• u get tested for a condition that could later develop in life

what is diagnostic genetic testing

• used to confirm diagnosis when symptoms are showing of a genetic condition

what are the two pre-natal genetic screenings

1. amniocentesis

2. chorionic villus sampling

what is amniocentesis

• when a needle gets sticked in a mom’s uterus and extracts the fluid that surrounds the fetus and the fluid has cells from the baby that can be tested to see if they have genetic disorder

what genetic disorder is this

• patau syndrome

what genetic disorder is this

• translocation down syndrom

what genetic disorder is this

• cri du chat

• some of 15 dleeted