Bio Unit 3: Genetic Diversity Flashcards
DNA name
Deoxyribonucleic acid DNA is a polynucleotide (a molecule composed of a chain of nucleotides)
Each nucleotide consists of
nitrogen base, sugar (deoxyribose), phosphate group
Nitrogen bases and who they pair with
adenine bonds to thymine (2H bonds)
guanine bonds to cytosine (3H bonds)
A molecule of DNA
is composed of two polynucleotide chains held together by hydrogen bonds between the bases. Phosphodiester hold each sugar to the phosphate group
Watson and Crick
discovered the structure of DNA in 1953, they won the nobel prize with Maurice wilkins in 1962
Rosalind franklin
work in x-ray crystallography was important in revealing the structure of the DNA molecule. The cross formed of dark spots indicated that the molecule had a helical structure
DNA has regions known as
genes that determine the phenotypical characteristics (traits) of an organism
An alteration in the DNA sequence is known as
a mutation
Mutations can be caused
by chemical agennts, UV radiation, natural causes (eg viruses), or during the process of replication
DNA replication
the structure of DNA allows it to be easily replicated (copied). The DNA molecule unzips and each side serves as a template. On each half of the molecule a new complementary half is built. The two new DNA molecules are identical to each other.
DNA must replicate
so that during cell division the new cells formed each recieve a complete set of genetic information
Cell must divide for
reproduction (unicellular organisms), growth (1 fertilized egg –> human of ~100 trillion cells), healing and tissue repair
Mitosis occurs when a parent
cell divides to produce two identical daughter cells
Mitosis refers
to the process of dividing the nuclear membrane
Cytokenesis refers to
the process of seperating the cytoplasm and its contents into equal parts
The cell cycle consists of
mitosis, cytokinesis, and interphase
Interphase
G1: cell growth
S: DNA is replicated
G2: cell prepares for mitosis
DNA is visible in the nucleus as strands called chromatin (uncoiled)
Phase 1 of Mistosis
Prophase: Prepare
Centrioles move to opposite poles of the cell, chromatin condenses and shortens into chromosomes, spindle fibers form between the centrioles, nuclear membrane starts to dissolve
Phase 2 of Mitosis
Metaphase: Middle
Spindle fibers attached to centrioles pull chromosomes into place, chromosomes line up across the equator of the cell, centromeres hold the chromosomes perpendicular to the spindle fibers
Phase 3 of Mitosis
Anaphase: Apart
Chromatids (single stranded chromosomes) separate at the centromere, chromatids are pulled to opposite poles by spindle fibers contracting
Phase 4 of Mitosis
Telophase: Two
Two nuclear envelopes form, single-stranded chromosomes uncoil to become chromatin, plant cell wall has to form between CANT DO CYTOKENESIS, Cytokensis occurs after telophase:
organelles are distributed between the two daughter cells and the cell membrane pinches inward
Mitosis vs meiosis
the purpose of mitosis is to maintain genetic continuity (the number of chromosomes in each daughter cell stays the same). The purpose of meiosis is to produce gametes (sex cells) which unite during sexual reproduction (the number of chromosmes in each sex cell is half of parent cell)
Asexual vs sexual reproduction
asexual: no meisosis
sexual: meiosisi
Asexual reproduction
a single parent gives rise to offspring that are genetically identical to the original parent (clones). Often produces many offspring rapidly. E.g. binary fission - amoeba, budding - yeast, fragmentation - sea stars, vegetative propagation - strawberries, spore formation - ferns
Sexual reproduction
genetic information from two parents is combined to produce a new organism (offspring are gentically different from parent). Require more time and energy than asexual reproduction. E.g. monarch butterflies live 3-4x longer when they don’t reproduce. Sexually reproducung organisms are better to adapt to hanging environments because of differences in individuals. Individuals that are better adapted will usrvive and perpetuate the species
Meiosis
In meiosis the cell goes through 2 stages of division. In meiosis 1, homogus pairs seperate (2 haploid cells are formed). In meiosis 2, sister chromatids seperate (4 haploid cells are formed).
Meiosis: Interphase
uncondensed chromatin, intact nuclear membrane
Meiosis: Early Prophase 1
Chromatin condenses and is visible as thin 2 stranded bivalents, Nuclear membrane disapears
Meiosis: Mid Prophase1
Chromosomes continue to condense and become visible as 4 stranded tetrads, the tetrad consists of two similar chromosmes one from each parent called homologous chromosomes, centriole duplicates
Meiosis: Late prophase 1
pieces of the homologoous pair break and exchange segments with other strands in crossing over, the structure is now called a chiasmata (when crossed, as many are cross-shaped)
Metaphase 1
Centrioles move to the poles, spindle fibers attach to the centromeres, homologous pairs are pulled ot the equator by spindle fibers
Anaphase 1
spindle fibers contract pulling apart the homologous pairs, double-stranded chromosomes are pulled to opposite poles, homologus pairs are separated
Telophase 1
the homologous pair of chromosomes is fully separated, nuclear membrane reappears, centrioles and spindle fibers disappear, sister chromatids remain togethr
Meiosis 2
Proceeds just like mitosis-but with half as many double-stranded chromosomes
The final product is 4 non-identical cells-each with single-stranded chromosomes due to independent assortment
Independent assortment-the random way chromosome line up at the metaphase plate
Each cell has a copy of every chromosome
Cells are haploid because they have one of each chromosome (not two copies like before meiosis)-haploid is not due to the chromosomes being single stranded (they are single stranded after mitosis when the cells are diploid)
SOme gametes may recieve all paternal chromosonmes or all maternal or a mix of each-it’s completely random
Random/independent assortment plus crossing over contributes to the variability produced by meiosis
Diploid (2n)
2 sets of information or chromosomes
All cells are diploid prior to meiosis
Haploid (n)
1 set of information or chromosmes
All cells are haploid after meiosis 1
In sperm formation
spermatogenesis, 4 sperm are produced, in the testes
In egg formation
oogenesis, 1 viable egg is produced with 3 polar bodies that will degrade, in the ovaries, unequal cytokenesis
Homologous chromosome pair
mom and dad copies of chromosomes
clevage furrow
bend in cell membrane
Random/Independent assortmen
during metaphase chromosomes align on the equator at random
Crossing over
allows for exchange of genetic information
Gameter
end of meiosis spermatids are formed which defferntiate into sperm cellls or eggs are formed which wait for ovulation.
Sperm formation
diploid spermatogonia-primary spermatocytes-4 haploid spermatids
egg formation
diploid oogonia-primary oocytes-1 haploid egg +3 haploid polar bodies
Mistakes in meiosis
through separation of chromosomes incorrect exchange of genetic information. Results in abnormal pairing during meiosis and zygote will have abnormal number of chromosomes
Nondisjunction
homologous chromosmes fail to move apart properly during meiosis I (anaphase, or sister chromatids during meiosis II (anaphase II)
Monosomy
only 1 copy of of a chromosome (1 copy is missing)
Trisomy
3 copies of a chromosomes (1 extra copy)
Abnormal chromosome structure
occur during crossing over, deletion, duplication, inversion, translocation
deletion
a chromosome fragment fails to reattach properly to the chromosmes involved
Duplication
if a segment reattaches to a complete homologue
Inversion
if a segment reattaches to correct homologue but in reverse orderra
translocation
if a segment attaches to a non-homlogous chromosome
What are genetic disorders
genetic disorders are health problems caused by abnormalities in the genome. They may be inherited or spontaneous. There are many possible causes and outcomes
Autosomal chromosome
non sex chromosome
Extra or missing autosomal chromosome
humans have 22 pairs of autosomal chromosomes, due to nondisjunctiion in meiosis 1 or 2. Monosomy of an autosome is always fatal. Some autosomal trisomy are also fatal. Some autosomal trisomy is fatal. Down syndrome
Extra or missing sex chromosome
the pair of sex (XX or XY) chromosomes are affected. Due to nondisjunction during meiosis 1 or 2. Monsomy of a sex chromosome can sometimes be letal (can survive with 1x, can’t survive with no x)
examples of sex chromosmes nondisjunction (3 tri, 1 mono)
XXX (triple x syndrome), XXY klinefelters syndrome, xyy jacob’s syndrome.
Mono: turner syndrome (x0)
Gene deletion
can occure to any gene or chromosome, due to crossing over during prophase 1. Cause many genetic disorders
Ecamples of gene deletions
wolf-hirschorn syndrome, partial deletion chromosome 4
Jacobsen syndrome, partial deletion on chromosme 11
Gene translocation
can occur to any gene on any chhromosome. Due to crossing over during prophase 1, cause many genetic disorder.
Example of gene translocation
xx male syndrome
Singel gene mutation
gene mutations change the sequece of nucleotides (A, T, C, and G). one or many nucleotides may be affected. Can occur during DNA replication during repair, due to viruses chemicals or radiation.
Examples of singal gene mutation
sickle cell anemia, cystic fibrosis, lactose intolerance
Multigene mutation
some traits are controlled by many genes. Mutations in multiple genes can that affect a trait and lead to a genetic disorder. Often seen in cancer cells.
Example of a multigene mutation
cancer
Mitochondrial dna mutation
remeber that mitochondria were once a free living cell that underwent endosymbiosis. Retains some DNA. Genes are for making atp
Example of mitochondrial dna mutations
kearns-sayre syndrome (energy organs)
Envirronmental factors
some genetic mutations always result in a genetic disorder. SOme genetic mutations only sometimes result in a genetic disorder. Genetics helps determine how the body responds to different environmental stimuli. Some environmental stimuli change gene expression
Epigenetics
the study of how your behaviors and environment can cause changes that affect the way your genes work. do not change the dna sequence but change how dna is read. Can be both inherited and influcenced by the environment
How are gmos created
take a gene from the organism with a desired gene and insert it into the DNA of another organism
benefits of gmo crops
resistant to: insects, viruses, herbicides
non-crop examples of gmos
pigs that are virus resistant, mosquitoes that carry a gene that kill their offspring, cows that make milk similar to human milk
how is reprodcutive cloning conducted
mature non sex somatic cell’s dna is injected into an egg cell without a nucleus
how is therapeutic cloning different?
somatic cells are reprogrammed to be come unspecialized cells in order to treat degernerative diseases or traumatic
what are negative effects for cloned animals
are often born with deformed organs live short painful lives
What is ivf
medical procedure: egg is fertilized by sperm in a test tube or anywhere outside the body
necessary steps to produce embryo in ivf
patient takes hormone meds to stimulate ovaries-multiple eggs per cycle
egss are retrieved and placed in lab
sperm are collected from donor
eggs+ sperm are mixed +fertilization, now embryo
can the embryos genetics be chosen
yes
How is prenatal genetic tesiting/screening conducted, how is the sample obtained
a thin needle is inserted through the women’s abdomen into the amniotic sac to withdraw a sample of fluid from around the devloping baby
whaat can be tested for with pgt
down syndrome, chromosome changes, anemia, cystic fibrosis
call all the fetuss genetic traits be tested for with pgt
no
What is the basis of the CRISPR Cas-9 system what in nature is it based on
based on the bacterial immune system, rmeber and destroy virsuses that infected them before
What can be done using crispr cas 9
target and modify typos in human genomes to treat genetic diseasecan
can crispr be used in living andimmals
yes
how is a dna fingerprint created
dna is collected from cells/samples. then mixed with an enzyme to produce dna framgents. then banding patters are visible and can be compared
what is dna fingerprint used for
identifiying crime suspects, dermining biological relationships, identifiying missing persons, identifying genetic disorders, tracking endangerec species
can you learn your specific genetic traits from a dna fingerprint
no
What is cloning? From a scientific standpoint, what procedures would be used to clone a human?
Cloning is the process of creating an identical copy of an organism, including its DNA. In the context of cloning a human, it typically involves somatic cell nuclear transfer (SCNT). This procedure involves taking a somatic cell (a cell that is not a sperm or egg cell) from the individual to be cloned and transferring its nucleus (which contains the DNA) into an egg cell from which the nucleus has been removed. The egg cell then develops into an embryo and can be implanted into a surrogate mother. The result is an organism genetically identical to the original organism.
Is cloning humans different procedurally from cloning animals? Are there any physiological risks to cloning humans? Are these risks different for animals? Why or why not?
The procedures for cloning animals and humans are largely the same, primarily relying on somatic cell nuclear transfer (SCNT). However, human cloning raises more ethical, moral, and legal concerns compared to animal cloning. Physiological risks for humans are believed to be greater due to the complexity of human development and the potential for more serious birth defects. Animals, such as sheep and cows, have been successfully cloned, but many cloned animals experience health issues, such as premature aging or organ defects. The risks for humans might be similar because the biological process is still new and unpredictable. Additionally, human cloning has not been practiced on a large scale and faces additional challenges due to the complexity of human biology.
- What is imprinting? What role does imprinting play in cloning humans? Animals?
Imprinting refers to a genetic phenomenon where certain genes are expressed in a parent-of-origin-specific manner. In some cases, either the mother’s or the father’s allele of a gene is expressed, while the other is silenced. This occurs through epigenetic modifications, which affect gene expression without changing the underlying DNA sequence. In cloning, imprinting is a major issue because clones may inherit the wrong pattern of gene expression. For example, a clone may have the genetic material of one individual, but if the imprinting is not correctly reprogrammed during the cloning process, the clone could exhibit abnormalities that would not normally occur in a naturally conceived child or animal. This is one of the reasons why cloned animals often have health issues.
How does cloning differ from sexual reproduction?
Cloning differs from sexual reproduction in that cloning produces an organism that is genetically identical to the donor organism, whereas sexual reproduction combines the genetic material from two different parents (one male and one female) to create a genetically unique offspring. In sexual reproduction, the process of meiosis (cell division that reduces the number of chromosomes) and fertilization result in genetic diversity. Cloning, on the other hand, involves the replication of genetic material from a single organism.
What role do meiosis and mitosis play in maintaining the integrity of the genetic code during cloning? Sexual reproduction?
Meiosis is crucial in sexual reproduction because it ensures genetic diversity by reducing the chromosome number by half, leading to the formation of sperm and egg cells. When fertilization occurs, the sperm and egg unite, creating a unique combination of genes.
Mitosis, on the other hand, is the cell division process that occurs in somatic cells and is used during cloning to create an exact copy of the original cell’s genetic material. In cloning, mitosis is used after the nuclear transfer to help the cloned embryo develop into a full organism. The genetic integrity is maintained in both processes, but in cloning, the genetic material is not subject to the variation that occurs in sexual reproduction.
Will Jason II be “identical” to Jason I? Why or why not?
Jason II, as a clone, would be genetically identical to Jason I in terms of DNA. However, he would not be a perfect replica of Jason I. Environmental factors, experiences, and random events during development (such as imprinting) can affect how genes are expressed, so Jason II may not have the exact same personality, interests, or even physical characteristics as Jason I. Even identical twins, who share the same genetic makeup, can differ in these respects.
What is the difference between a somatic cell and a sex cell?
A somatic cell is any cell in the body that is not a reproductive cell (not a sperm or egg cell). These cells contain a full set of chromosomes (in humans, 46 chromosomes).
A sex cell (or gamete) is a reproductive cell, either a sperm cell (from males) or an egg cell (from females). These cells contain half the number of chromosomes (23 in humans), which combine during fertilization to form a new organism with a full set of chromosomes.
