DNA

Question 1

What is DNA

Answer 1

Molecule responsible for hereditary

Question 2

Four bases + pairs

Answer 2

adenine, thymine, guanine, cytosine
A –> T
G –> C

Question 3

two functions of DNA

Answer 3

1) replication 2) direct synthesis of proteins

Question 4

Steps of replication

Answer 4

goal) pass genetic info to new cells
1) occurs during cell division
2) helix unzips separating base pairs
3) 2 strands unwind and each attract appropriate bases to construct its complement.
4) two identical DNA molecules are created

Question 5

Steps of synthesis

Answer 5

Transcription: DNA is copied into mRNA.

mRNA leaves the nucleus and goes to a ribosome.

Translation: The ribosome reads mRNA in groups of 3 bases (codons).

tRNA brings matching amino acids.

Amino acids join together to make a protein.

Question 6

central dogma

Answer 6

explains how genetic information flows inside a cell. flows from DNA to messenger RNA (mRNA) to
protein

Question 7

Transcription

Answer 7

DNA is copied into mRNA.
The enzyme RNA polymerase helps match RNA bases to DNA bases
The mRNA then leaves the nucleus and goes to a ribosome.

Question 8

Translation

Answer 8

The ribosome reads the mRNA in groups of three bases (called codons).

Each codon tells which amino acid to add.

tRNA brings the correct amino acids to the ribosome.

The amino acids join together to form a protein chain.

Question 9

mRNA vs tRNA

Answer 9

mRNA – single stranded and carries coding sequence for protein
tRNA – transfers amino acids to ribosomes

Question 10

codon

Answer 10

A sequence of 3 nucleotides on mRNA that carries the genetic code for an amino acid during protein synthesis.

Question 11

anticodon

Answer 11

A sequence of 3 bases on tRNA that binds to the mRNA codon, ensuring the correct amino acid is brought to the ribosome.

Question 12

introns

Answer 12

non coding region of gene thats removed during RNA splicing

Question 13

exons

Answer 13

parts of genes that are spliced back together

Question 14

alternative splicing

Answer 14

mRNA spliced to create different transcripts which are then translated into different proteins and is used to produce many proteins

Question 15

General characteristics of the human genome

Answer 15

consists of about 3.2 billion base pairs; contains about 21,000 to 25,000 protein-coding genes, which range in size from 1000 bases to 2 million bases

Question 16

three main surprises of the human genome project

Answer 16

1) most of the genome is non coding
2) we have small number of protein coding genes
3) two humans share 99.9% of DNA

Question 17

Diff kinds of genetic variations in individuals

Answer 17

Sequence variation: A difference in the DNA base sequence (A, T, C, or G).

Example: A single base change → SNP (single nucleotide polymorphism)

Structural variation: A difference in the amount of DNA — extra or missing segments.

Types

Deletion: a segment of a chromosome is missing

Duplication: a segment of a chromosome is repeated

Organizational variation: A difference in how DNA is arranged or organized.

Types:

Inversion: a segment of a chromosome is reversed end to end

Translocation: segments of DNA are exchanged or rearranged between non-homologous chromosomes

Question 18

Mutations

Answer 18

Occurs when mistakes are made in copying DNA and results in different alleles

Question 19

Chars of human chromosomes

Answer 19

Total chromosomes: 46 (or 23 pairs)
Autosomes: 22 pairs → carry most of our genes
Sex chromosomes: 1 pair (XX or XY) : XX = female,XY = male

Centromere: The “pinched” center area, Has no genes, Holds the chromosome together during cell division
p arm:The short arm (above the centromere)
q arm: The long arm (below the centromere)

Banding patterns:
Each chromosome has unique light/dark bands used to locate genes
Example: Huntington’s disease gene → 4p16

Question 20

Human vs animal chromosomes

Answer 20

Species Number of Chromosomes
Humans 46 (23 pairs)
Fruit flies 4
Mice 20
Dogs 39
Carp (fish) 52
Great apes (chimpanzee, gorilla, orangutan) 48 (24 pairs)

Question 21

Somatic vs Gametes

Answer 21

Somatic = body cells, diploid (46)

Gametes = sex cells, haploid (23)

Question 22

mitosis

Answer 22

cell division not involved in production of gametes

Question 23

meiosis

Answer 23

occurs in the sex cells of ovaries and testes to produce eggs and sperm

Question 24

Common Chromosomal problems

Answer 24

breaks that lead to inversion, deletion, duplication, translocation

inversion: a segment of chromosome is reversed end to end
deletion/duplication: segment of chromosome is deleted/duplicated
Translocation: parts between two nonhomologous chromosomes are rearranged

Question 25

epigenetics

Answer 25

changes in gene expression that do not change the DNA sequence. It literally means “on top of the genes.”

Question 26

Types of epigenetics

Answer 26

1) X inactivation: Early in embryonic development, one X chromosome in each cell is randomly inactivated. Only happens to females 2) Genomic (Gametic) Imprinting: Means that some genes are expressed only from one parent’s copy. 3) DNA Methylation: Addition of a methyl group (–CH₃) to DNA (usually on cytosine bases).This blocks access to genes → turns them off.

Question 27

why are tortoise and calico cats always female + mixture of furs

Answer 27

The fur color gene is on the X chromosome. One X has the orange allele, the other has the black allele. Random X inactivation → some cells express orange, others black → mosaic coat pattern. Males (XY) only have one X, so they can be orange or black, not both

Question 28

genetic mechanisms leader to prader willi and angelman

Answer 28

Gametic imprinting: If the deletion is from the mother’s chromosome → Angelman syndrome Symptoms: severe mental retardation, awkward gait, frequent laughter If the deletion is from the father’s chromosome → Prader-Willi syndrome Symptoms: overeating, obesity, short stature, temper issues

Question 29

influence of maternal diet affected the agouti mouse

Answer 29

Normal agouti mice are yellow and obese. When pregnant mothers were fed a methyl-rich diet, their offspring had: More DNA methylation Brown fur and normal weight This shows that maternal diet can change gene expression without changing DNA sequence.