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[start]
[q] What is heredity?
[a] the transmission of traits from one generation to the next
[q] What is variation?
[a] Any difference between individuals of the same species.
[q] What is genetics?
[a] The scientific study of heredity and variation
[q] What are genes?
[a] a unit is hereditary information, specific nucleotide sequences in DNA
[q] What is an allele?
[a] specific variation of a gene on a specific spot on a chromosome
[q] What is Meiosis?
[a]
1. Meiosis is VERY similar to mitosis, but they are also very different
2. Meiosis is the creation of gametes, which are sex cells (sperm or egg in humans).
3. Meiosis goes through PMAT twice, so it has prophase 1 and prophase 2, metaphase 1 and metaphase 2, etc.
4. this results in four daughter cells
5. happens in testicles or ovaries in humans
Gametes can also be pollen, spores, and other things in various organisms
[q] describe gametes
[a]
1. gametes are sex cells that make up sperm, eggs, pollen, spores, etc.
2. gametes are haploid cells, which means they have a half set of DNA (chromosomes). This is because the DNA in a sperm cell combines with the DNA in an egg cell during sex to make a zygote, which is diploid (full set of DNA).
3. The DNA in your body cells (somatic cells) is all identical, while the DNA in your gametes varies per cell; this is one reason why a child will inherit different traits depending on which of your sperm/egg it comes from.
4. Some of the DNA from your dad and some from mom is in your gametes, while your body cells have all the DNA your mom and dad gave you.
[q] Describe the differences between mitosis and meiosis
[a]
Mitosis:
creates 2 daughter cells
creates identical cells
creates diploid cells
creates body (somatic) cells
PMAT x1
Meiosis:
creates 4 daughter cells
creates different cells
creates haploid cells
creates gametes
PMAT x2
[q] What happens in prophase 1?
[a] 1. nuclear envelope dissolves
2. Chromatin turns to chromosomes
3. Homologous chromosomes (chromosomes that code for the same genes from mom and dad) pair up
4. Crossing over: When the homologous chromosomes pair, they will probably touch and trade some of their DNA, so chromosomes will have DNA from both parents.
[q] What happens in metaphase 1?
[a] 1. Centrioles go to poles
2. Random assortment: homologous pairs align in the middle randomly
3. spindle fibers attach
[q] What happens in anaphase 1?
[a] homologous chromosomes are pulled apart
[q] what happens in telophase 1?
[a] 1. Nucleus reforms
2. cleavage
3. cytokinesis
[q] What happens in prophase 2?
[a] 1. spindle fibers appear
2. Nuclear envelope dissolves
[q] What happens in metaphase 2?
[a] 1. Chromosomes align in the middle
2. centrioles go to poles
3. spindle fibers attach
[q] what happens in anaphase 2?
[a] sister chromatids pull apart
[q] What happens in telophase 2?
[a] 1. Nucleus reforms
2. cleavage
3. cytokinesis
[q] What is the result?
[a] 4 different daughter cells
[q] What are ways that meiosis creates genetic diversity?
[a]
1. Independent assortment: In metaphase 1, homologous chromosomes are split randomly, creating diversity in genes passed on
2. Crossing over: homologous pairs exchange genetic information
3. Haploid cells: when two haploid cells combine to form a zygote after sex, it ensures something new will be made
[q] What fundamental processes suggest that all organisms share common ancestry?
[a]
1. All organisms have DNA/RNA, which suggests we all have shared genetic information
(some viruses are an exception and only have DNA or RNA)
2. Ribosomes are in all lifeforms
3. Major features of genetic code are shared by all modern living systems.
This means that the same sequence of bases will code for the same amino acids.
(for example, the sequence ATG will always code for methionine)
[q] Explain alleles on chromosomes
[a]
1. Alleles are specific variants of genes. For example, a flower might have an allele for purple or white petals.
2. Alleles are located at a locus, which is a specific spot on a chromosome that codes for the same trait. The allele for purple petals would always occur on the locus for petal color
3. If alleles at a locus differ, one will be dominant, and that one will be expressed.
The dominant allele is often represented by a capitol letter and the recessive will be represented by a lowercase letter
[q] Explain the Law of Segregation
[a]
The law of segregation states that because of independent assortment, there is a 50/50 chance that either allele will be passed down.
HH will pass down H to their offspring
Hh will pass down H or h to their offspring
hh will pass down h to their offspring
[q] Explain the terms heterozygous and homozygous
[a]
1. Heterozygous: different alleles, one dominant and one recessive (Hh)
2. Homozygous: Same alleles, dominant or recessive (HH or hh)
[q] Explain the terms genotype and phenotype
[a]
1. Genotype: the alleles you have. so HH, Hh, and hh are all genotypes
2. Phenotype: The trait expressed. so a white flowers phenotype is white
3. If H is for purple (dominant) and h is for white (recessive), a flower with the genotype Hh will have a purple phenotype
[q] What is a monohybrid cross?
[a]
A type of Punnett Square that reveals the probability of different genotypes for one trait
for example:
AA x Aa has a 100% probability of expressing the A gene
Aa x aa has a 50/50 chance of expressing the A or a gene
Aa x Aa has a 75% chance of expressing A and a 25% chance of expressing a
[q] What is a dihybrid cross?
[a]
A chart that reveals the probability of two different traits
the chart here crosses AaBb x AaBb
[q] What is co-dominance?
[a]
1. When one allele is not dominant over the other and both are expressed
2. An example of this is blood types, that’s why instead of just having A, B, or O type blood, you can have AB as well because neither type A or B are dominant over each other. O is recessive, so a parent with AB cannot have an O offspring.
[q] What is incomplete dominance?
[a]
A blending of traits. Black+white=gray
so of B is black and b is white…
BB will be black
Bb will be gray
bb will be white
[q] What are linked genes?
[a]
1. Linked traits exist on different loci (plural of locus) on the same chromosome
2. Since these traits are on the same chromosome, they tend to be inherited together. The only way they won’t be inherited together is because of crossing over
3. Dihybrid crosses don’t work on linked traits
[q] what are sex linked genes?
[a]
1. Sex linked genes exist on the X or Y chromosomes that determine sex
(this is almost always the X chromosome rather than Y because the Y chromosome is so small)
2. Recessive traits on the X chromosome effect males more than females because males only have one X chromosome.
3. This means that if a mother is homozygous recessive (hh) for an X linked trait, her son will always have it because a males X chromosome is always from the mom, but a daughter might not have it
A common example of this is hemophilia, a recessive X linked trait that males are more susceptible to
[q] What is is called when multiple genes code for one trait?
[a]
1. A polygenic trait.
2. Traits like skin color are polygenic, so they are not as simple as black or white, there will be a gradient
[q] What is non-nuclear inheritance?
[a] 1. Genes that are inherited from DNA found in places other than the nucleus like the mitochondria or chloroplasts, which have their own DNA
2. DNA from mitochondria and chloroplasts is only passed down from the mother.
3. This means that a male cannot pass down a trait that comes from mitochondrial DNA, but a female will always pass down a trait from mitochondrial DNA
[q] How can the environment effect phenotype?
[a]
1. Some traits exhibit phenotypic plasticity, which means they can change based on weather, age etc.
2. some common examples of this is hair color changing with age, skin color changing from sun exposure or fur color changing with the seasons.
[q] What us non-disjunction?
[a]
1. When a spindle fiber grabs two chromosomes instead of one in metaphase 1 of meiosis, causing an extra or fewer chromosome
2. This can cause disorders such as Down Syndrome or mess with gender chromosomes. It can also lead to death
3. If a person ends up with 2 of the 21st chromosomes, they will have down syndrome
4. A persons gender chromosomes could be XXY, XYY, XXX, just X, or just Y. This can lead to hormonal issues, infertility, or death.
[q] Genome
[a] The genetic material of an organism or virus
[q] Somatic Cells
[a] body cells
[q] Gametes
[a] reproductive cells
[q] Mitotic (M) Phase
[a] mitosis and cytokinesis
Mitosis: Cell separates and divides chromosomes
Cytokines: Cell divides cytoplasm and organelles.
[q] Interphase
[a] Cell grows, replicates chromosomes, produces new organelles and cyclins.
[q] Mitotic Spindle
[a] a structure made of microtubules that controls chromosome movement during mitosis
[q] Centrosome
[a] A structure that functions as the microtubule organizing center and is important during cell division, has two centrioles.
[q] Kinetochore
[a] A structure within the centromere containing the motor protein dynein. Moves the chromosomes apart during anaphase.
[q] Cell Cycle Control System
[a] A cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle.
[q] Cyclin
[a] a protein that regulates the cell cycle
[q] CDK
[a] (Cyclin-dependent kinases) A protein kinase that is active only when attached to a particular cyclin. Activity rises and falls depending on the concentration of the cyclin partner.
[q] MPF
[a] (Maturation-promoting factor) a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase.
[q] growth factors
[a] Regulatory proteins, ensure that cell division occurs properly
[q] Density Dependent Inhibition
[a] crowded cells stop dividing
[q] Prophase
[a] Chromosomes become visible, nuclear envelope dissolves, spindle forms
[q] Metaphase
[a] Chromosomes line up in the middle of the cell
[q] Anaphase
[a] the chromatids (Mitosis) or homologous chromosomes/chromatids (Meiosis) separate and move toward opposite poles
[q] Telophase
[a] The chromosomes begin to stretch out and lose their rodlike appearence. A new nuclear membrane forms around each region of chromosomes.
[q] Cytokinesis in plants
[a] cell plate forms
[q] Cytokinesis in animals
[a] Cleavage furrow forms
[q] Binary Fission
[a] one cell divides to form two identical cells
[q] Karyotype
[a] A display of the chromosome pairs of a cell arranged by size and shape.
[q] homologous chromosomes
[a] Chromosomes that have the same sequence of genes, though may have different alleles (versions) of those genes. Maternal/Paternal
[q] Sex Chromosomes
[a] X and Y chromosomes.
[q] Autosomes
[a] non-sex chromosomes
[q] Diploid
[a] 2 sets of chromosomes
[q] Haploid
[a] having a single set of unpaired chromosomes
[q] Fertilization
[a] Fusion of an egg and sperm cell
[q] Zygote
[a] diploid fertilized egg
[q] Crossing Over
[a] exchange of genetic material between homologous chromosomes during prophase I of meiosis
[q] Tetrad
[a] structure containing 4 chromatids that forms when homologs pair during meiosis
[q] True Breeding
[a] have identical alleles of a given gene/ homozygous
[q] Hybridization
[a] The cross of two true-breeding parents. (BB x bb)
[q] P generation
[a] Parental Generation
[q] F1 generation
[a] offspring of the P generation
[q] F2 generation
[a] offspring of the F1 generation
[q] Alleles
[a] Different forms of a gene
[q] Punnet Square
[a] A chart that shows all the possible combinations of alleles that can result from a genetic cross
[q] Homozygous
[a] having two identical alleles for a trait. BB or bb
[q] Heterozygous
[a] having two different alleles for a trait. Bb
[q] Phenotype
[a] physical characteristics of an organism (blue eyes)
[q] Genotype
[a] genetic makeup of an organism (bb)
[q] Mendel’s Law of Segregation
[a] Alleles segregate from one another during the formation of gametes. (due to independent assortment)
[q] Monohybrid
[a] A cross between individuals that involves one pair of contrasting traits
[q] Dihybrid Cross
[a] a cross between individuals that involves two pairs of contrasting traits
[q] law of Independent Assortment
[a] non-linked genes separate into gametes independent of one another in meiosis
[q] Codominance
[a] A condition in which both proteins produced by the alleles for a gene are fully expressed. (spots/stripes)
[q] Incomplete Dominance
[a] Cases in which one allele is not completely dominant over another. The two proteins produced by the alleles mix. (blended colors)
[q] Multiple Alleles
[a] A gene that has more than two alleles, like blood type (A,B,O)
[q] polygenetic inheritance
[a] many genes are involved in specifying traits that exhibit continuous variation (ie. a normal/bell-shaped curve). Ex: Human height, skin color
[q] Pedigree
[a] A diagram that shows the occurrence of a genetic trait in several generations of a family.
[q] Cystic Fibrosis
[a] autosomal recessive disorder resulting in thick mucous in the respiratory tract.
[q] Sickle Cell Disease
[a] autosomal recessive disorder resulting in mutated hemoglobin molecules that polymerize and cause misshapen red blood cells.
[q] Huntington’s disease
[a] autosomal dominant disorder resulting in neurodegeneration, leading to dementia and death.
[q] Wild Type
[a] An individual with the normal (most common in nature) phenotype. Ex: red eyes in fruit flies
[q] Mutant
[a] An individual with a mutated form of an allele, not common in nature. Ex: white eyes in fruit flies
[q] Linked genes
[a] Genes located adjacent on the same chromosome that tend to be inherited together in genetic crosses.
[q] X inactivation
[a] one of two X chromosomes in a female is randomly inactivated and remains coiled as a Barr body
[q] Nondisjunction
[a] Error in meiosis in which homologous chromosomes fail to separate.
[q] Aneuploid
[a] Abnormal number of chromosomes.
[q] Monosomatic
[a] Only has one copy of a chromosome
[q] Polyploid
[a] condition in which an organism has extra SETS of chromosomes
[q] Deletion
[a] removes a chromosomal segment
[q] Duplication
[a] repeats a segment
[q] Inversion
[a] reverses a segment
[q] Translocation
[a] moves a segment from one chromosome to another
[q] Down Syndrome
[a] (Trisomy 21) Occurs when an individual has 3 chromosomes of the 21st pair instead of 2; caused by NONDISJUNCTION
[q] Turner Syndrome
[a] A chromosomal disorder in females in which either an X chromosome is missing ( making the person XO instead of XX) or part of one X chromosome is deleted.
[q] Extranuclear Genes
[a] genes found in organelles in the cytoplasm; inherited maternally (mitochondria in the egg)
[q] DNA methylation
[a] The addition of methyl groups to bases of DNA after DNA synthesis; may serve as a long-term control of gene expression.
[q] locus
[a] Location of a gene on a chromosome
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