1-DNA, Genes, and chromosomes

Question 1

what is DNA

Answer 1

a long, double-stranded, spiral-shaped molecule that stores the cell’s genetic info

• contains codes for building and maintaining an organism
• structure looks like a winding staircase!
• the steps are composed of nitrogenous base pairs
  
  • the bases pair with each other
  • each base is attached to a sugar molecule and phosphate molecule

Question 2

what is a nucleotide

Answer 2

nitrogenous base + sugar molecule + phosphate molecule
basic building block of DNA and RNA

Question 3

gene

Answer 3

small section of DNA that codes for a protein
- we have between 20k-25k genes in each of our cells!!
- the genes vary in size from a few hundred bases to OVER 2,000,000 BASES!
- however… number of genes is NOT a measure of complexity

Question 4

why is how DNA is transcribed and translated important?

Answer 4

• the sequence of steps encodes the instructions for PROTEINS
• if there’s a change in the sequence, it can potentially change the amino acid produced
• may affect the protein’s function

Question 5

mutation

Answer 5

a change in the sequence of nucleotides in the DNA
- may be as small as a change in one nucleotide/step
- may affect multiple genes

Question 6

when may mutations be caused?

Answer 6

• mistakes when DNA is replicating, most of the time
  
  • or… environmental factors (UV light) that damage dna

Question 7

allele

Answer 7

different versions of the same gene/DNA sequence that arise due to mutations/changes in the sequence of nucleotides

• responsible for variation in inherited traits
• why? mutations can prevent one of more proteins from functioning properly

Question 8

GENOME

Answer 8

the complete set of genetic info found in an organism’s cell
- includes an organism’s complete set of DNA and its genes
- typically measured in number of bases or base-pairs (bp)
- genome size is not necessarily a measure of complexity

Question 9

CHROMOSOMES

Answer 9

it is a structure made up of a single long DNA molecule(s) and histone proteins

human genome consists of 23 pairs of chromosomes, PLUS!! the small chromosomes in the cells’ mitochondria

Question 10

chromatin

Answer 10

DNA-protein complex
when chromosomes are not tightly coiled

Question 11

autosomes

Answer 11

-non-sex chromosomes
- humans have 22 pairs of AUTOSOMES
- numbered 1-22 by size from largest to smallest
- 1 being the biggest
- determine somatic characteristics

Question 12

SEX CHROMOSOMES

Answer 12

1 pair, Involved in determining an individual’s sex
XX = female
XY = male

Question 13

CENTROMERE

Answer 13

each chromosome has: a constriction point called the centromere
its the ball in the middle of the x
divides chromosome into 2 arms

Question 14

locus

Answer 14

specific location of a gene
genetic street address!
loci = plural

Question 15

difference between drawn replicated and unreplicated chromosome structures

Answer 15

unreplicated - one double-stranded DNA molecule + histone proteins
replicated chromosome - often drawn in an x shape

Question 16

sister chromatids

Answer 16

replicated DNA, consists of 2 identical chromatids
should carry the same allele

Each chromatid = one DNA molecule

two sister chromatids that are attached at the centromere = one chromosome

after mitosis: daughter chromosomes

Question 17

HOMOLOGOUS CHROMOSOMES

Answer 17

aka: homologs

• same size
• same centromere location
• same carried genes in the same locus
• BUT!!! They do not necessarily carry the same same alleles!!

Question 18

PLOIDY

Answer 18

The number of sets of chromosomes in a nucleus

Question 19

haploid

Answer 19

one set of chromosomes (n)

Question 20

diploid

Answer 20

2 sets of chromosomes (2n)

Question 21

polypoloid

Answer 21

many sets of chromsomes (triploid is 3n)

Question 22

haploid number

Answer 22

number of different/ unique chromosomes in a cell (n)

number of chromosomes in the gamete (egg or sperm) of a diploid organism

for human somatic cells:
2n=46

Question 23

GENOTYPE

Answer 23

refers to the set of alleles present at one or more specific loci