Ch 4 - genetics Flashcards
biology :(
What are homologous chromosomes?
two genetically SIMILAR chromosomes, one from each parent
Random segregation of one member of each homologous pair of chromosomes into games defines…
Law of independent assortment
Chromosomal basis of down syndrome
Trisomy 21
karyotype has a total of 47 chromosomes
If diploid number is 14, haploid number is…
7
What events contribute to genetic diversity
independent assortment
crossing over
random fertilization of gametes
After telophase 1, chromosomal makeup of each daughter cell is…
haploid, and the chromosomes are each composed of two chromatids
tetrads of chromosomes are aligned at the equator of the cell; alignment determines indep assortment defines…
metaphase 1
Recombinants
crossed over genes
Prophase 1
Homologous pairs pair up
crossing over
spindle forms
Metaphase 1
chromosomes pair line up at the equator randomly
Law of indep assortment
the homologous pairs line up randomly; adds gen. variety
Anaphase 1
homologous pairs separate
When can nondisjunction happen?
Anaphase 1 or 2
When is nondisjunction more damaging?
Anaphase 1 - will result in all 4 cells being wrong
Law of segregation
separating conflicting alleles
nondisjunction
when homologous pairs/chromatids stick together and results in gametes with a wrong number of chromosomes
telophase 1
cell pinches in and separates into 2 HAPLOID cells
In prophase 2, does it start with the homologous partners?
no- homo pairs were separated in anaphase
Metaphase 2
single chromosomes line up in middle of the cell (opp as before)
anaphase 2
sister CHROMATIDS separate (like mitosis)
telophase 2
both 2 cells linch inward and form a total of 4 haploid genetically diff cells
In the ovary, the cells divide unevenly and…
3 will form polar bodies and 1 egg that will receive most of the cytoplasm so it can nourish the developing embryo for fertilization
Why do gametes need to be haploid?
when they join, the baby will have the correct diploid number
What is Reduction Division
Reduction of one diploid cell into 2 haploid cells and then divides those 2 cells into 4 haploids
XX
female
XY
male
XXY
Klinefelter Syndrome (2n +1) - results in sterility, female sex characteristics; male
X
Turner Syndrome (2n-1) - results in sterility, petite/short, not strong
Missing part of chromosome
Cri Du chat syndrome - crossing over is not reattached properly
Trisomy 18
Edward Syndrome -
Who was the first to analyze patterns of inheritance and create the two laws in gens
Gregor Mendel
P gen, F1, F2
parents, kids, grandkids
Testcross
mating between individual of unknown genotype and a homozygous recessive indv
(e.g. P_ x pp)
sex-linked
carried on X chromosome
e.g muscular dystrophy, color blindness, hemophilia, baldness
pleiotropy
impact of a single gene on more than one characteristic (e.g sickle cell disease)
Polygenic inheritance
combined effects of 2+ genes on a single characteristic (e.g skin color)
incomplete dominance
Blended phenotype
e.g.
HH = red
Hh = pink
hh = white
co-dominance
Both alleles show up
e.g.
HH = red
Hh = red and white
hh= white
recessive disorders
albinism, cystic fibrosis, sickle cell, ect
dominant disorders
Achondroplasia (dwarfism), alzheimers, huntingtons
invasive fetal testing
amniocentesis, CVS, fetoscopy
noninvasive fetal testing
ultrasound imaging
Gene linkage
alleles that STAY together on the same chromosome the whole time (e.g. red hair and freckles)
