DNA, RNA, & Meiosis DNA, RNA, & Meiosis ReviewReview

DNA, RNA, & Meiosis DNA, RNA, & Meiosis ReviewReviewCPBiologyCPBiology

Ms. MorrisonMs. Morrison

1. Diagram and label a model of DNA. Include the parts that make up a single nucleotide.

• 3 parts to nucleotide:– 5 carbon sugar

(deoxyribose)– Phosphate group– Nitrogenous base

(A, T, C, and G)

2. Describe in detail how DNA replicates itself.

1. DNA molecules unzips into two strands2. Complementary nucleotides pair with the

two strands3. DNA polymerase binds the nucleotides

together and “proofreads” the DNA4. Two new DNA strands – each with one

original strand and one new strand

(Note: prokaryotes starting replicating at one single point, while eukaryotes start replicating at many points)

3. Differentiate between DNA and RNA.

Difference DNA RNA

Bases thymine (T) uracil (U)

Sugars Deoxyribose Ribose

Appearance double strand (double helix)

single strand

4. Compare DNA and RNA by checking the appropriate box:

DNA mRNA

tRNA rRNA

Deoxyribonucleic acid √Ribonucleic acid √ √ √Ribose present √ √ √Deoxyribose present √Phosphate present √ √ √ √

4. Compare DNA and RNA by checking the appropriate box:

DNA mRNA

tRNA rRNA

Adenine present √ √ √ √Thymine present √Uracil present √ √ √Guanine present √ √ √ √Cytosine present √ √ √ √

4. Compare DNA and RNA by checking the appropriate box:

DNA

mRNA

tRNA rRNA

Made of nucleotides √ √ √ √Double stranded √Single stranded √ √ √Remains in the nucleus √Contains a chemical message or code

√ √

5. List the main function for each of the following types of RNA:

1. mRNA – contains instructions for assembling amino acids into proteins from DNA

2. rRNA – make up ribosomes along with proteins

3. tRNA – transfers amino acids to ribosome as specified by DNA

6. Summarize the process (steps) of transcription.

1. RNA polymerase binds to DNA2. RNA polymerase separates DNA

strands3. One strand of the DNA is used as a

template to make complementary mRNA strand

4. mRNA strand edited before leaving nucleus with message to code for proteins

7. Summarize the process (steps) of translation.

1. The mRNA strand attaches to ribosome.2. Start codon on mRNA (AUG) is read and

tRNA with anticodon attaches the amino acid (methionine).

3. The next tRNA with the correct amino acid binds to the 2nd mRNA codon.

4. The ribosome forms a peptide bond between the two amino acids.

5. The mRNA strand moves through the ribosome binding amino acids to the growing polypeptide chain.

6. When the stop codon is reached on the mRNA strand, the mRNA strand and the completed protein is released from the ribosome.

7. Summarize the process (steps) of translation.

7. Summarize the process (steps) of translation.

8. Determine the mRNA, tRNA, and amino acid sequence for the following DNA strand.

DNA TAC AAA CCA TTG CGA AAT AGA TGA ATT

mRNA AUG UUU GGU AAC GCU UUA UCU ACU UAA

tRNA UAC AAA CCA UUG CGA AAU AGA UGA AUU

Amino acid

Methionine

Phenylalanin

e

Glycine

Asparagine

Alanine

Leucine

Serine

Threonine

STOP

9. Contrast gene and chromosome mutations.• Gene mutations affect the DNA sequence

which will change the protein that the gene codes for. There are two types:– Point mutations – single base substituted for another

so only one amino acid affected– Frameshift mutation – single base added or deleted

so all amino acids changed after mutation • Chromosome mutations affect the entire

chromsomes and all the genes located on it, examples:– Extra copy of a chromosome– Only one copy of a chromosome instead of two

(homologous)– Missing part of chromosome or have extra genes

attached

10. Explain why some changes in DNA structure are inherited and some are not.

Only changes that occur in gametes (egg or sperm cells) can be passed on to offspring (inherited). If the changes occur in body cells, then only that organism is affected.

11. Identify which type of mutation has occurred in the original DNA sequence. Underline all the mutated codons.

DNA: TAC TTA CCG TCA ATT

a. TAC TCT ACC GTC AAT T frameshift mutation (insertion)

b. TAC TTA CGT CAA TT frameshift mutation (deletion)

c. TAC TTA CCG ACA ATT point mutation

12. Diagram the phases of meiosis in an animal cell with 4 chromosomes. Explain what happens in each phase.• Meiosis I (with one cell)

– Prophase I – homologous chromosomes (replicated during Interphase I) pair up in tetrads while spindle forms and nuclear membrane disappears, crossing over can occur

– Metaphase I – homologous chromosomes line up in middle of cell and spindle fibers attach to them

– Anaphase I – homologous chromosomes are pulled to opposite sides of cell by spindle fibers

– Telophase I – nuclear membrane reforms around the separated homologous chromosomes, spindle breaks down, cell divides into two haploid cells

12. Diagram the phases of meiosis in an animal cell with 4 chromosomes. Explain what happens in each phase.

12. Diagram the phases of meiosis in an animal cell with 4 chromosomes. Explain what happens in each phase.

• Meiosis II (with two cells)– Prophase II – nuclear membranes disappear and

spindle forms (no DNA replication occurs during Interphase II)

– Metaphase II – sister chromatids (chromosomes) line up along center of cell and are attached to spindle fibers

– Anaphase II – sister chromatids are separated and pulled towards opposite sides of the cell

– Telophase II – nuclear membranes reform around the chromatids and the spindle breaks down, the two cells divide into four haploid cells

12. Diagram the phases of meiosis in an animal cell with 4 chromosomes. Explain what happens in each phase.

13. How do the results of meiosis differ in female organisms from male organisms?

• Males – one gamete forms four sperm cells in even meiotic divisions

• Females – one gamete forms one egg cell with most of the cytoplasm and three polar bodies which are NOT used in reproduction, this occurs because of uneven meiotic divisions

14. Differentiate between haploid and diploid cells. Using a human cell, explain how the number in each are different.• Diploid means having two homologous

chromosomes – similar chromosomes where one is from the male parent and the other is from the female parent

• Haploid means having a single chromosome (only from one parent)

• Humans have 23 pairs of chromsomes for a total of 46 chromosomes – this is diploid

• Human gametes (eggs, sperm) have 23 chromosomes (therefore when egg and sperm combine – a cell is produced with 46 chromosomes or 23 pairs of chromosomes)

15. Compare mitosis to meiosis.

Mitosis MeiosisKind of cell used body cell germ cellKind of cell made (diploid or haploid)

diploid haploid

# of cells made two four# of chromosomes in daughter cells compared to original cell

same # (diploid)

half the #(haploid)

Number of cycles

one division two divisions

15. Compare mitosis to meiosis.

Mitosis Meiosis

Differences in Interphase

DNA is replicated so duplicate copy for division

I – DNA replicated so duplicate copies of chromosomesII – NO replication

Differences in Prophase

Nuclear membrane disappears, spindle forms, chromosomes become visible

I – same as mitosis, but tetrads form between homologous chromosomes pairs and crossing over can occurII – same as mitosis

15. Compare mitosis to meiosis:

Mitosis Meiosis

Differences in Metaphase

Sister chromatids line along center of cell and are attached to spindle fibers

I – similar to mitosis but it is the homologous chromosome pairs that line up II – same as mitosis

Differences in Anaphase

Sister chromatids are separated and pulled to opposite ends of cell

I – Homologous pairs are separated and pulled to opposite ends of cellII – same as mitosis

15. Compare mitosis to meiosis:

Mitosis Meiosis

Differences in Telophase

Nuclear membranes reform around separated chromatids, spindle breaks down, and cell divides – two diploid daughter cells formed

I – same as mitosis, but is a duplicated chromosome and when the cell divides each daughter cell is haploidII – same as mitosis but two cells divide to form four haploid cells