Study Questions Set 3 Flashcards
The human gametes have about 3 billion bp of DNA in their chromosomes. a) if the entire DNA was in relaxed B-DNA, what is the length of 1 chromosome in a cell? b) on average how many complete turns would be in a chromosome? c) if there are 30-40k genes in a gamete, how many genes are there in the average chromosomes?
a) 3 billion bp/DNA * 1 DNA/23 chromosomes * 0.34 nm/bp * 1m/10^9nm = 0.044m
b) 0.044m * 10^9nm/m * 1 turn/3.4nm = 13,043, 478 turns
c) 35000/23 = 1521
Define homologous chromosomes
chromosomes that contain the same genes in the same gene order but with different alleles
Define non-homologous chromosomes
chromosomes that contain different genes
how many chromosomes in a germ cell?
23
distinguish between homologous chromosomes and sister chromatids.
homologous chromosomes have the same genes in the same gene order with different alleles, but sister chromatids have the same genes in the same gene order with the same alleles. sister chromatids are identical
what is the purpose of cell division in prokaryotes and eukaryotes?
prokaryotes: reproduction
eukaryotes: tissue growth, cell repair, reproduction
distinguish between dna replication and cell division
dna replication happens in S phase, it is the process in which cells will duplicate their chromosomes
cell division happens in the M (mitotic) phase, it is the process by which one cell splits into 2, where chromosomes are divided up between the 2 daughter cells
distinguish between the reasons for mitosis and meiosis
mitosis is for tissue growth, cell replication, essentially any time we want identical daughter cells
meiosis is used for the reduction of chromosome and produces variability in the 2 daughter cells, important for the organism to evolve and whatnot
how is the variability of genetic information attained by meiosis and fertilisation?
meiosis allows for the independent assortment of homologous chromosomes, which means there is a difference in chromosomes that end up in the daughter cells
it also allows for recombination, where the dsDNA of one chromatid will be replaced by one more fragment of another chromosome
fertilisation is the combination of two completely different chromosome sets through the fusion of gametes
what is cell cycle? and what are the stages?
cell cycle is a set of events that take place in creating daughter cells from one parent cell
the stages are interphase (G1, S, G2) and mitotic phase and cytokinesis
list and briefly describe the checkpoints in cell division
G1 checkpoint: checks if the DNA is damaged, checks if the cell is grown enough
G2 checkpoint: checks if the DNA replicated properly
M checkpoint: checks about the spindle, if the chromosomes are properly aligned (if not, mitosis will stop)
M checkpoint: cell division will stop if the chromosomes are not properly divided
all trying to stop the creation of damaged cells that will either be useless or harm the organism
what can trigger arrest in the cell cycle?
damage to the cell, DNA replicating more than once, improper separation of chromosomes, cell dividing before replication is complete, cell mass not the right size
how many chromosomes are there in the somatic cell of a person with down’s syndrome? a) how many autosomes? b) how many sex chromosomes does this person have in a somatic cell? c) germ cell? d) gamete? e) spermatozoid? f) ovum? g) zygote?
a) 45 b) 2 c) 2 d) 1 e) 1 f) 1 g) 2
how many DNA molecules does a person with Down’s have a) in mitotic metaphase? b) in G1?
a) 94 b) 47
how many telomeres are there in a person’s somatic cell in G2?
188
