Genes, Alleles, Homologous Chromosomes

Question 1

What is a gene

Answer 1

• Small segment of DNA

Question 2

What is an allele

Answer 2

Alternative version of a specific gene (upper or lower case letters)

Question 3

Where do our alleles come from, how many

Answer 3

1 from mom, 1 from dad

Question 4

What is a haploid cell

Answer 4

N, 1 copy of each gene and chromo, 23 chromosomes

Question 5

What is a homologous chromosome

Answer 5

• Pairs similar in size and shape
• carry same genes
• 1 from mom, 1 from dad
• genes code for same thing

Question 6

What are the steps in Meiosis

Answer 6

1) interphase
2) Meiosis 1
3) Meiosis 2

Question 7

What does Meiosis 1 do

Answer 7

• reduces ploidy by separating homologous chromosomes
• diploid (2n) germ cells divide into 2 haploid (n) daughter cells

Question 8

Meiosis 2

Answer 8

• Maintains equal ploidy by separating sister chromatids
• haploid cells from meiosis 1 divide, produce genetically diverse haploid cells

Question 9

What are the steps of meiosis 1

Answer 9

Interphase

1)prophase 1
2)metaphase 1
3) anaphase 1
4) telophase 1

Cytokinesis

Question 10

What is prophase 1 in meiosis

Answer 10

• same as mitosis (nucleolus and nuc membrane disappear, spindles attach to kinetechore, centrioles continue separating
• DIFFERENT: homologous pairs line up with other homologous pairs forming Tetrads

Question 11

What is a synapsis

Answer 11

Process where a pair of homologous chromosomes are held tightly together by proteins and crossing over occurs

Question 12

What is crossing over

Answer 12

Paired homologous chromosomes share genetic materiel between non-sister chromatids

Question 13

In what phase does crossing over occur

Answer 13

Prophase 1

Question 14

What is the chiasma

Answer 14

Site of crossing over

Question 15

What happens in metaphase 1 off meiosis

Answer 15

Homologous chromosomes are paired and aligned in 2 rows in the middle of the cell (metaphase plate)

Question 16

What happens in anaphase 1 of meiosis

Answer 16

• both copies of homologous pairs are separated , chromatids remain attached

Question 17

What happens in telophase 1

Answer 17

• chromosomes drawn to opp ends of the cell
• chromatids still attached by centromere
• nuclear membrane surrounds chromosomes
• nucleoli reappear

Question 18

What happens in Cytokinesis after Meiosis 1

Answer 18

• each daughter cell has both copies of one of each kind of chromosome, so reduced from diploid to haploid

Question 19

What happens in Meiosis II

Answer 19

• sister chromatids separate

Question 20

What is special about sister chromatids after crossing over (after prophase 1)

Answer 20

They are no longer identical

Question 21

What happens in anaphase 2

Answer 21

• Centromeres break
• chromosomes drawn to opposite ends of the cell

Question 22

What happens in telophase 2

Answer 22

• nuclear membrane and nucleoli form

Question 23

What happens in cytokinesis after meiosis 2

Answer 23

• each cell divides, giving 4
• each cell now have 1 chrom instead of 2

Question 24

What is independant assortment , when does it occur

Answer 24

• metaphase 1
• pairs of homologous chromosomes independently and randomly align, results in enormous amount of possible genetic combinations during meiosis

Question 25

What is non disjunction

Answer 25

Error that occurs during meiosis 1 or 2 , chromosomes fail to separate - results in aneuploid cels , cells containing too many Orr too little chromosomes

Question 26

what are the cells that produce sperm called

Answer 26

spermatocytes (produced by mitosis)

Question 27

what are the cells that produce eggs called

Answer 27

oocytes(produced by mitosis)

Question 28

what would happen if we didnt reduce the ploidy of sex cells during meiosis

Answer 28

number of chromosomes would always double

Question 29

what is random fertilization

Answer 29

genetic variabilty: any sperm can fuse with any ovum