Unit 3: Genetic Continuity Section 1

Question 1

What is DNA

Answer 1

-is a nucleic acid
-contains genetics that determine our inherited traits
-is a long molecule tightly wrapped into chromosomes

Question 2

Structure of DNA

Answer 2

-shaped as a double helix (twisted ladder)
-“Steps of the ladder”~made of nitrogenous bases
-“Handles of the ladder”~made of a phosphate group attached to a ribose sugar called the sugar phosphate backbone

Question 3

What are Nitrogenous bases

Answer 3

-Steps of DNA
-the 2 types are… Pyrimidines (Adenine (A) and Guanine (G)) and Purines Cytosine (C) and thymine (T)

Question 4

Which nucleotides bind

Answer 4

-Adenine and thymine bind to create steps
-Guanine and cytosine bind to create steps
- the steps are called nucleotides

Question 5

Structure of MRNA

Answer 5

-“m” stands for messenger
-is a nucleic acid made from the DNA molecule
-single helix
-has uracil instead of thymine

Question 6

Making mRNA

Answer 6

-called transcription

Question 7

What is translation

Answer 7

RNA—>Protein
After RNA is transcribed from DNA it can be used to make proteins that make physical
-tRNA brings in amunio acids that corespond with your starting nucleotides

Question 8

What is replication

Answer 8

-making DNA
-process is semi-conservative because when a new double helix is made it consists of one of the old strands

Question 9

Steps of Replication

Answer 9

1. Initiation
   -Dna unwinds using helicase, DNA unzips and hydrogen bonds are broken
2. Elongation
   -DNA polymerase binds nucleotides to the strands of the unzipped DNA
3. Termination (proof-reading)
   -Ligase corrects any mistakes in the replication and seals the DNA

Question 10

What is Meiosis

Answer 10

-cell division in reproductive cells (egg and sperm)
-makes cells haploid so the zygote can have the correct amount of chromosomes

Question 11

Chromosomes of sex cells

Answer 11

-they have 22 autosomes (non sex determining chromosomes)
-1 sex chromosome
-females have xx
-males have xy

Question 12

Phases of meiosis 1

Answer 12

1. Interphase
2. Prophase
3. Metaphase 1
4. Anaphase 1
5. Telophase 1
6. Meiosis 2

Question 13

Phases of meiosis 2

Answer 13

1. Prophase 2
   -centrioles replicate, no interphase
2. Metaphase 2
   -centrioles to the poles, spindle fibres, chromosomes line up in the middle
3. Anaphase 2
   -cleavage begins, centrioles shorten spindle fibres, chromosomes split at the centromere
4. Telophase 2
   -cytokinesis, nucleus reforms around chromatids
   -you now have 2 haploid cells

Question 14

What is Down’s syndrome

Answer 14

-chromosomal disorder
-caused by trisomy of the 21st chromosome
-symptoms: short stature, developmental delays

Question 15

Mitosis (what, steps)

Answer 15

-cell division of non sex cells
-Interphase: G1: cell grows, S: replication of chromosomes, G2: prep for mitosis, centrioles replicate
-Prophase: -Chromosomes shorten, nucleus dissapears
-metaphase: Centrioles to the poles, chromosomes line up in the middle, spindle fibres
-anaphase: cell elongates, chromatids are pulled apart
-telophase: Cytokinesis (cell splits), nucleus reforms, 2 cells are formed

Question 16

Interphase (meiosis 1)

Answer 16

-first step
-chromosomes replicate
-centrioles replicate
-nucleus disappears

Question 17

Prophase (meiosis 1)

Answer 17

-homologous chromosomes (similar) pair
-pairs make 4 sister chromatids (tetrads), this step is called crossing over
-Non-sister chromatids cross over each other and exchange segments of chromosomes
-crossing over allows for genetic variation 3

Question 18

Metaphase (meiosis 1)

Answer 18

-centrioles to the poles
- spindle fibres attatch to homologous pairs
-pairs line up at the center randomly (random assortment) which allows for genetic variation

Question 19

Anaphase (meiosis 1)

Answer 19

-homologous pairs are pulled to opposite poles

Question 20

telophase (meiosis 1)

Answer 20

-cytokinesis
-both daughter cells are diploid with 2 copies of DNA

Question 21

Turner’s syndrome

Answer 21

-monosomy of the X chromosome
-egg with no X chromosome is fertilized by a sperm with an X chromosome
-symptoms: female appearance, brown spots on body, poor development of secondary sex characteristics

Question 22

Klinefelters syndrome

Answer 22

-Trisomy of sex chromosomes
-person inherits 2 x and 1 Y chromosome

Question 23

Gametogenesis

Answer 23

-formation of sex cells during meiosis

Question 24

Spermatogenesis

Answer 24

-spermatogonium undergo meiosis to be haploid

Question 25

Oogenesis

Answer 25

-oocyte undergoes meiosis to create one haploid/viable ova and 3 polar bodies which aren’t viable

Question 26

Abnormal meiosis (non-disjunction)

Answer 26

-mistake in meiosis
-non disjunction is when 2 homologous chromosomes move to the same poles
-this makes 1 daughter cell 2 chromosomes and 1daughter cell to be missing 1 chromosome

Question 27

DNA and protein synthesis

Answer 27

-Happens in the cytoplasm
1.Transcription: Dna unwinds to create separate strands
-1 stand acts as a template for RNA synthesis
-complementary nucleotide is matched
2.Translation:mRNA leaves nucleus and attaches to the ribosome
3. Continued: tRNA attaches to the a- site of the ribosome, the p-site (to make room for another tRNA) and to create a link of amino acids, and the e-site where it will detach
-cycle repeats

Question 28

Base pair substitution

Answer 28

-Changes the amunio acid
-swapping the nucleotide

Question 29

Codons and anti-codons

Answer 29

Codons: the three letter codes in DNA
Anti-codons:the complementary 3 letter codes that tRNA introduces

Question 30

Frameshift mutation

Answer 30

A deletion or insertion that leads to a shift in the DNA