Flashcards in Intro to Medical Genetics Deck (64)
A gene is a segment of DNA that encodes for a specific
e) all of the above
Define an allele
Alternative forms of a gene (DNA at a specific locus) that differ in sequence
Define a locus
A physical region of a chromosome; often used to refer to a segment of DNA that contains a specific gene
Homologous chromosomes are chromosomes that ______ during meiosis, ____ from each parent
Are homologous chromosomes identical?
No, normally only a few base pair differences in each gene
Are sister chromatids identical?
Yes, two identical duplicated chromosomes joined by a single centromere
During which cell replication cycle would you find sister chromatids?
What are autosomes?
ANy chromosome that is not a sex chromosome
An organism with 4 copies of each chromosome would be ________
A human has 45 chromosomes in a cell. He is a _____________ (type of ploidy)
A human has 69 chromosomes in a cell. He is a ____________ (type of ploidy)
Euploid - abnormal but still same number of each homologous chromosome
Germline cells are responsible for _____________________
production of gametes
What are gametes
haploid germ cells (sperm and ova)
What are zygotes
Two gametes fuse (during fertilization), diploid
Homologous chromosomes have _______ genes in ______ positions, but _______ alleles
same, same, different
Why is neonatal screening done?
To ID rare disorders that can cause brain damage or death if not treated early ie PKU
Describe prophase of mitosis
chromatin condenses (chromosomes with two chromatids) --> spindle forms --> nucleolus breaks down
Describe prometaphase of mitosis
spindle invades nuclear region, chromosomes move to equatorial plane
Describe metaphase of mitosis
Chromosomes at equatorial plane and centromeres divide
Describe anaphase of mitosis
poles move apart and chromosomes move towards destinations
Describe telophase of mitosis
Spindle breaks down --> chromatid uncoils --> nucleoli formed --> contractile ring causes cytokinesis
What is the product of cytokinesis in mitosis?
Two daughter cells, each genetically identical to parent cell
Describe prophase I of meiosis
Homologous chromosomes pair up and exchange fragments (cross over)
Describe metaphase I of meiosis
Homologous pairs line up at metaphase plate
Describe Anaphase I of meiosis
Homologues separate to opposite ends of cell, sister chromatids stay together
Describe Telophase I of meiosis
Newly formed cells are haploid, each chromosome has two (non-identical) sister chromatids
Meiosis II is very similar to mitosis. What are the two differences?
1) Haploid (2n) cells at beginning rather than diploid (4n)
2) Creates 4 haploid cells, with chromosomes having one chromatid each
What is the key difference between meiosis and mitosis?
During prophase homologous chromosomes synapse - pair up tightly and there is genetic exchange (evidenced by chiasmata)
Pairs of sister chromatids align according to homologous sequences and are bound together --> crossing over occurs