Lecture 3: Topic 1 Flashcards
what are chromosomes made up of
DNA and protein
what is chromatin
wrapped around protein
are humans diploid or haploid, and why
diploid (2n)
because we get 2 of each chromosome, 1 from each parent
n (haploid number)
23 chromosomes
2n (diploid number)
46 chromosomes
characteristic of the two copies of each chromosome in human cells
homologous
what do you call different versions of a gene, and what do these do
alleles
promote different traits (ex. curly or straight hair)
how do cells get the right number of chromosomes
through cell division
duplicating the cell components and separating the material into 2 daughter cells
what cell components are duplicated during cell division
- organelles
- cytoplasm
- chromosomes
what are the 2 main parts of the cell cycle
- interphase
- cell division
what steps is interphase made up of
G1
S
G2
what step is cell division made up of
mitosis (M)
what is G1
growth
the cell grows and increases the volume of its proteins and organelles
what is S phase
synthesis
this is when the cell copies all of its DNA
what is G2 phase
gap/growth
the cell continues to grow in both its proteins and its DNA
what are the stages of mitosis
prophase
metaphase
anaphase
telophase
why do diploid organisms need to have specialized sex cells
sex cells (sperm or egg) allow traits to be combined from two organisms
how many of each chromosome do gametes have
one of each
what is the name of the special type of cell division that gametes require
meiosis
what (in general) does meiosis do
takes diploid cells (2n) and divides them into gametes (n)
where does sexual reproduction (meiosis) occur
the testis or ovaries
how can a cell end up with an incorrect number of chromosomes
the chromosomes do not separate correctly during mitosis or meiosis
how does maternal age affect birth issues
as maternal age increases, incidences of birth defects increase
what is the relationship between nondisjunction and age, and why
happens more as you age, because bonding of chromosomes gets weaker with age
what are the 3 different types of down syndrome
trisomy 21
mosaicism
translocation
trisomy 21
95% of all cases
3 complete copies in all cells
mosaicism
1-2% of all cases
3 copies in some but not all cells
translocation
3-4% of cases
partial copy of chromosome 21 attached to another chromosome
how is down syndrome detected
karyotyping
what is karyotyping
- isolate chromosomes during fetal cell division
- arrange in pairs according to size
aneuploidies
word that means in general having an extra or 1 less than chromosome
what percentage of conceptions terminate in spontaneous abortion
20%
what percentage of spontaneously aborted fetuses demonstrate some form of chromosomal imbalance
30%
large percentage of fetuses demonstrating chromosomal abnormalities are ________
aneuploid
monosomies
monosomies are not often found in spontaneously aborted fetuses, which suggests that monosomic gametes may be very functionally impaired
diagnostic testing used in genetic counseling
amniocentesis (15-18 weeks)
chorionic villus sampling (CVS) performed 10-12 weeks
