Genetic Processes Flashcards
What is a somatic cell?
A plant or animal cell that forms the body of the organism; excludes reproductive cell
What are the three functions of cell division?
~growth of the organism
~repair of tissues and organs that have been damaged
~maintenance to replace dying or dead cells
How long does the cell cycle take?
For most healthy, actively dividing animal cells, the cell cycle takes about 12 to 24 hours
Which cells last the longest and shortest amount of time?
Stomach cells last a few hours and nerve cells last 60 years
What are the 6 stages of the cell cycle?
1) interphase
2) Prophase
3) Metaphase
4) Anaphase
5) Telephase
6) Cytokenisis
Phases 2 through 6 are Mitosis. It replicates DNA (nucleus) 5-10% of cells are in these phases.
What happens in Interphase?
Between 90-95% of cells are in interphase.
at the end of interphase it double its DNA
What happens in Prophase?
~nuclear membrane disappears/disintegrates, chromosomes are now free in the cytoplasm and are more susceptible to disease (i.e. cancer)
~chromatin shortens and thickens to become visible chromosomes
What happens in Metaphase?
chromosomes line up on the equator of the cell
What happens in Anaphase?
centromere splits, so each sister chromatid gets pulled to opposite poles of the cell
What happens in Telephase?
a nuclear membrane reappear (2–>1 for each pole) chromosomes become chromatin
What happens during cytokenisis?
Dividing cytoplasm with all organelles
- *in plants the rectangular cell indents in the middle (cell plate) in preparation for dividing**
- *in animals the circular shaped cell indents in the middle (cleavage furrow or “pinch”) to prepare for the cell dividing**
whats the analogy for DNA and protein?
DNA=cookbook/recipe
Protein= cookie
What is an Autosome?
a chromosome that is not involved in determining the sex of an organism
~Autosomes are chromosomes #1-22
what are sex chromosomes?
an X or Y chromosomes, which determines the genetic sex of an organism
the 23rd pair of chromosomes —> males: XY
–>females:XX
girls have 23 macthing pairs of chromosomes and boys have 22 matching pairs and an XY
What are homologous chromosomes?
they are pairs of chromosomes that appear similar, in terms of their length, centromere location, and banding pattern when stained with certain dyes. They contain the same sequence of genes as another chromosome.
homologous chromosomes are not identical
What is an allele?
a different form of the same gene.
~these different forms account for the differences in specific traits, such as brown hair versus blonde hair
~represented by letters, capitals are dominant and lower case are recessive
What is a gene?
a part of a chromosome that governs the expression of a trait and is passed on to offspring; it has a specific DNA sequence
What is a karyotype?
a photograph of pairs of homologous chromosomes in a cell
~take a blood sample; look for white blood cells during mitosis (metaphase) and take a picture of the chromosomes
~enlarge the photo, place it in a gel-like substance, then cut out all the chromosomes, pair them up and place them in order, and label them
~this checks genetic diseases and can tell gender of the body
What is a gamete?
a male or female reproductive cell
What is a zygote?
a cell formed by the fusion of two gametes
What is fertilization?
in humans, the joining of male and female haploid gametes
What is a haploid cell?
a cell that contains half the number of chromosomes as the parent cell (from the Greek word meaning single)
What is a diploid cell?
a cell that contains pairs of homologous chromosomes (from the Greek word meaning double)
What is meiosis?
the cellular process that produces cells containing half the number of chromosomes as the parent cell. The process that produces gametes with a haploid number of chromosmes
What is synapsis?
the aligning of homologous chromosomes during prophase 1 in meiosis 1. This forms tetrads
What are the two key outcomes of meiosis?
~ Genetic Reproduction: meiosis is a form of cell division that produces daughter cells with half the number of chromosomes of the parent cell
~Genetic Recombination: the products of meiosis have different combinations of alleles. Genetic recombination gives rise to offspring that are genetically different from one another and their parents. This greatly increases the genetic variation in a population. “shuffling the genetic deck”
What is the difference between Mitosis and Meiosis?
~mitosis consists of only one set of division phases. Meiosis consists of two sets of division phases.
~Mitosis produces two diploid daughter cells that are identical. Meiosis produces four haploid daughter cells that are identical
~Meiosis is important for organisms, like humans, because it results in genetic variation, which allows for genetic diversity within a population
What are the two ways genetic variation is ensured?
1) by the creation of gametes that carry different combinations if maternal and paternal chromosomes, in a process called INDEPENDENT ASSORTMENT (random assortment)
2) by the exchange of genetic material between maternal and paternal chromosomes, in a process called CROSSING OVER
What is crossing over?
it is the exchange of chromosomal segments between a pair of homologous chromosomes. Up to ten different cross overs can occur per pair (tetrad)
~during synapsis in Prophase 1, non-sister chromatids cross over and exchange segments of DNA to produce a new combinations of genes on a chromosome
What is independent assortment?
The chromosomes line up on the equator randomly, not in any order, and maternal and paternal cells aren’t in a particular order
What is one reason for diversity?
~each chromosome has a 50% chance of being from the father (P) or mother (M). Because Maternal and paternal chromosomes are sorted randomly
~since you are the product of two sex cells (egg and sperm) your genetic (chromosomal) combination is (1/2)X23 X (1/2)X23, which gives you about a 1 in a trillion chance of having an identical twin
What are mutations?
~deletions/additions/substitutions: the triplet is missing a letter or has an extra letter so it develops a non-functional protein
~it could create a harmful (toxic) protein
~no protein at all may be made
Sex Chromosome abnormalities:
~the high frequency of people with sex chromosome aberrations is partly due to the fact that they are rarely lethal conditions
~a single Y chromosome is sufficient to make a male while its absence makes a female. Female abnormalities are due to the variation in the number of X chromosome. Male abnormalities are the result of irregular numbers of either the X or Y chromosomes or both
What is monosomy?
The loss of a chromosome as a result of non-disjunction
What is trisomy?
The gain of an extra chromosome as a result of non-disjunction
What is amniocentesis?
a sample of amniotic fluid (fluid surrounding the fetus), which contains fetal cells, is taken after the 14th week of pregnancy
What is Chorionic Villus Sampling (CVS)?
A sample of cells from the chorion (part of the placenta) is taken after the 9th week of pregnancy
How can you diagnose genetic disease?
1) Pedigree
2) Karyotyping
3) Blood Test (for particular protein)
4) DNA Probe Test
What is a pedigree?
you look for family history of diseases
What is karyotyping?
~white blood cells, halt cell division at metaphase
~photograph chromosomes, rearrange in pairs (largest to smallest)
~chromosome defects visible
What is a Blood Test?
~carriers (heterozygus) will often have less of the correct protein (only one copy of the gene) or more of a defective protein
~Tay Sach’s carriers- less of enzymes required to break up lipids
~e.g. PKU babies-blood from heel-high pheryiket onuria
- *up until 2008 we only tested for 2 DNA defects, in 2008 they added the 28th test**
- *ontario was referred to as the 3rd world regime of testing because we only had 2 tests, whereas saskatchewan was doing 29 and New York was doing 44**
What is a DNA probe test?
~for some diseases, DNA’s sequence of defective gene is known
- complementary DNA probe is made
- labelled with radioactive markers
- if a person’s DNA becomes radioactive (probe sticks) they have the defective gene
- e.g. sickle cell, cystic fibrosis, DMD, hemophilia, PKU, Huntingtons
What is selective breeding?
the process of breeding plants and animals for desirable traits
What is artificial insemination?
the process by which sperm are collected and concentrated before being introduced into the females reproductive system
What is an embryo transfer?
the process by which an egg that has been fertilized artificially is transferred into a recipient females uterus
What is in vitro fertilization?
the technique used to fertilize egg cell’s outside the female’s body. “test tube babies”. First one was born in Britain on July 25, 1978.
this technology is moving so quickly that the laws can’t keep up
What is cloning?
a process that produces identical copies of genes, cells or organisms
What is gene cloning?
the use of DNA manipulation techniques to produce multiple copies of a single gene or segment of DNA
What is recombinant DNA?
a molecule of DNA that includes genetic material from different sources
What is therapeutic cloning?
the process of replacing an egg cell’s nucleus with the nucleus from a somatic donor cell to produce a cell line of genetically identical cells
What is reproductive cloning?
the process of producing genetically identical organisms
What is a Stem Cell?
an undifferentiated cell that can develop and become specialized into different cell types of the body
What is ART?
Assisted Reproductive Technology
What disease is found on human chromosome number 4?
Huntington’s disease
What disease is found on human chromosome number 5?
Cri du chat
What disease is found on human chromosome number 7?
Cystic fibrosis
What disease is found on chromosome number 12?
PKU
What diseases are found on human chromosome number 15?
Prader-willi and tach-Sachs
What diseases are found on human chromosome X?
- duchenne muscular dystrophy
- baldness
- boy in the bubble
- colour blindness (red and green)
- hemophilia A
What disease is found on human chromosome Y?
SRY
What is Trisonomy 21?
Down syndrome
