AP Bio Unit 5
How do you calculate recombination frequency?
(# of recombinants / total # of offspring) (100%)
What is polyploidy?
- 2n+ complete sets of chromosomes - Triploid (3n) or tetraploid (4n) - Rare in animals, frequent in plants (wheat, strawberries)
What happens in Telophase ll?
- 4 haploid cells - nuclei reappear - each daughter cell genetically unique
What are the different types of prenatal testing?
- Amniocentesis - the liquid around the fetus is removed and tested - Chronic villus sampling (CV's) - a sample of the placenta is removed and tested - Ultrasound - allow fatal health to be assessed visually in utero
What is recessive
- An allele that only sometimes expresses itself - Homozygous Recessive = aa
AP Classroom - Why do scientists use hypothesis testing?
Scientists use hypothesis testing to determine if investigative results are due to independently variable or due to chance
AP Classroom - What are sex-linked traits?
Sex-linked traits are traits determined by genes located on sex chromosomes.
Males receive only _______ copy of the gene on the X chromosome to express the trait
1
What are sex-linked genes?
- Some traits are determined by genes on sex chromosomes (X and Y) - Females XX, Males XY - Sex-linked (or X-linked) genes reside on sex chromosomes (X in humans) - Y-linkage is rarely encountered since chromosome is so small
Who is Gregor Mendel?
- Austrian Monk - Brought experimental and quantitative approach to genetics - Bred pea plants to study inheritance - Why peas? - Control mating (self vs. cross pollination) - Many varieties available - Short generation time
What is Blood Transfusion?
- Blood transfusions much match blood type - Mixing of foreign blood → clumping → death - Rh factor - protein found on RBC's (Rh+ = has protein, Rh- = no protein)
What is Tay-Sachs disease?
- Caused by a nucleotide insertion - Lysosomes lack the functional enzyme to break down certain fats (glycolipids) - When these fats accumulate in the nerve cells of the brain, brain cells die & death usually follows early in childhood - A recessive disorder (both parents past mutated allele)
What is Sickle Cell Anemia?
- Caused by a nucleotide substitution - Production of defective hemoglobin, the oxygen-carrying protein in RBC's - RBC's become sickle shaped - RBC's do not flow through capillaries freely & oxygen is not adequately delivered throughout the body (anemia) - Homozygous individuals (sickle cell disease): inadequate oxygen supplies can lead to oxygen damage, bone abnormalities and impaired mental functioning - Heterozygous individuals (sickle cell trait): generally without symptoms (the normal allele produces enough normal hemoglobin)
What is Huntington's disease?
- Caused by the insertion of multiple repeats of 3 nucleotides - The mutated gene codes for a defective enzyme - Results in the death of nerve cells in the brain - A dominant disorder (only 1 parent needs to pass the defective allele)
What are chromosomal mutations and the different types?
- Caused when chromosome segments are changed - Types: - Inversion - chromosomal segment breaks & reattaches in reverse order - Deletion - chromosome segment is deleted - Duplication - chromosome segment is copied 1 or more times - Translocation - chromosome segment breaks and reattaches to another chromosome
What is crossing over?
- Crossing over produces recombinant chromosomes which combine genes inherited from each parent - Crossing over begins very early in prophase l, as homologous chromosomes pair up gene by gene - Homologous portions of 2 non sister chromatids trade places - Crossing over contributes to genetic variation by combining DNA from 2 parents into a single chromosome
What is Chronic myelogenous leukemia (cancer)?
- Due to a translocation of chromosome 9 and 22 - Translocated chromosome 22 (Philadelphia chromosome) - Takes place in a single bone marrow cell that will form a tumor that leads to cancer
What is the Law of Independent Assortment?
- Each pair of alleles segregates (separates) independently during gamete formation - Ex.) color is separate from shape
What is incomplete dominance?
- F1 hybrids have appearance that is between that of 2 parents - ex.) red RR X white rr = pink flowers Rr
How simple single gene traits can be influenced by the environment
- Flower color in some species of plants is dependent upon the pH of the environment - Soil pH influences flower color in certain species of hydrangea - Flower color is blue when the soil pH is acidic & pink when the soil pH is basic
What is Independent Assortment of Chromosomes?
- Homologous pairs of chromosomes orient randomly at metaphase l of meiosis - In independent assortment, each pair of chromosomes sorts maternal and paternal homologues into daughter cells independent of the other parts - The number of combinations possible when chromosomes assort independently into gametes is 2^n, where n is the haploid number - For humans, n=23, there are more than 8 million (2^23) possible combinations of chromosomes
What are Conserved Features in Organisms?
- It is assumed that the most recent common ancestor to all life had traits which allowed it to be successful - These traits were passed onto offspring from generation to generation - The most recent ancestors to all organisms must have had DNA, RNA, ribosomes, and core metabolic pathways (ex.glycolysis) - These processes and features are conserved in all organisms
What are linked genes?
- Linked genes tend to be inherited together - They are located near each other on the same chromosome
What are polygenic traits?
- Many traits are the product of multiple genes acting in combination - Polygenic Inheritance - the interaction of many genes to shape a single phenotype - Certain traits are displayed as a continuous variation - Ex.) eye color, hair color, skin color, height and weight
How an increased exposure to UV radiation in humans stimulates a corresponding increase in melanin, the skin-darkening pigment
- Melanin absorbs UV light, which protects skin cells from DNA damage to a point - The increased exposure to UV light leads to increased melanin production & darker skin color
How seasonal changes in daylight length influences the expression of hair color from brown (in summer) to white (in winter) in the snowshoe hare
- Melatonin is a hormone that triggers the melanin gene (for production of melanin pigment) to turn off - During winter, low levels of sunlight cause animals to produce more melatonin, which works to turn off the melanin gene - This leads to a white coat
What is the Multiplication Rule?
- Probability that 2+ independent events will occur together in a specific combination → multiply probability of each event - Probability of this "AND" that - ex.) probability of throwing 2 sixes: - (⅙) (⅙) = 1/36 - ex.) probability of having 5 boys in a row: - (½) (½) (½) (½) (½) = 1/32 - ex.) if cross AABbCc X AaBbCc, probability of offspring with AaBbcc is: - (½) (½) (¼) = 1/16
What is the Addition Rule?
- Probability that 2+ mutually exclusive events will occur → add together individual probabilities - Probability of this "OR" that - ex.) chances of throwing a die that will land on 4 or 5: - ⅙ + ⅙ = ⅓
What is Random Fertilization?
- Random fertilization adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg) - The fusion of 2 gametes (each with 8 million possible chromosome combinations from independent assortment) produces a zygote with about 64 trillion diploid combinations - Crossing over adds even more variation - Each zygote has a unique genetic identity
What is non-nuclear inheritance?
- Some traits result from non-nuclear inheritance - Chloroplasts & mitochondria are randomly assorted to gametes & daughter cells - In animals, mitochondria are transmitted by the egg & not by sperm so mitochondrial DNA is maternally inherited - In plants, mitochondria and chloroplasts are transmitted in the ovule and not in pollen so mitochondrial and chloroplast DNA is maternally inherited
What is a monohybrid cross?
- Study 1 character - ex.) flower color
What is a dihybrid cross?
- Study 2 characters - ex.) flower color and seed shape
How temperature influences sex determination in various reptiles
- Tempeatures experienced during embryonic development determine the sex of offspring - Eggs incubated at lower temperatures become males; those at higher temperatures become females
What is a Test Cross?
- Used to determine if a dominant phenotype is homozygous or heterozygous (ex: PP or Pp) - Cross with a homozygous recessive (ex: pp)
What is dominant?
- Will always exhibit the dominant trait - Capital letter - Heterozygous Dominant = Aa - Homozygous Dominant = AA
What is a zygote?
- a fertilized egg (2n) - divides by mitosis to make multicellular diploid organism
What are point mutations and different types?
- a single nucleotide in the DNA of a gene is incorrect - Types: - Substitution - a different nucleotide is substituted for the correct one - Insertion - an extra nucleotide is added - Deletion - a nucleotide is omitted
What is aneuploidy?
- abnormal # of chromosomes - Monosomic (1 copy → 2n-1) - Trisomic (3 copies → 2n+1)
What is a pedigree chart?
- diagram that shows the relationship between parents / offspring across 2+ generations - Women = O - Man = ▢ - Trait Expressed = ⬤⬛
What are multiple alleles?
- gene has 2+ alleles - ex.) human ABO blood groups - Alleles = I^A, I^B, I - I^AI^B = codominant
What is a linkage map?
- genetic map that is based on % of crossover events - 1 map unit = 1% recombination frequency - 50% recombination = far apart on same chromosome or on 2 different chromosomes
What is sexual reproduction?
- meiosis produces gametes (sex cells) - 2 parents: male / female - lots of variation / diversity - slower and energy consumptive - ex; humans, trees
What happens in Prophase ll?
- no interphase or crossing over - spindle forms
What is Phenotypic Plasticity?
- occurs when organisms with the same genotype exhibit different phenotypes in different environments - Ex.) in humans, weight & height are examples of complex traits that can be influenced by environmental conditions - Availability of food and proper nutrition will allow a person to grow taller - Overeating & lack of exercise will allow for weight gain
What happens in Anaphase l?
- pairs of homologous chromosomes are separated - sister chromatids still attached by centromere
What is codominance?
- phenotype of both alleles is expressed - ex.) red hairs X white hairs = roan hoards
What is asexual reproduction?
- produces clones (genetically identical) - single parent - little variation in population (only through mutations) - fast and energy efficient - ex; budding, binary fission, mitosis
What happens in Prophase l?
- synapsis - homologous chromosomes pair up - tetrad - 4 sister chromatids - crossing over at the chiasmata
Babies Jane (blood type B), John (blood type O), and Joe (blood type AB) were mixed up in the hospital who are their parents? Couple #1: A,A Couple #2: A,B Couple #3: B,O
1 = Joe 2 = Jane 3 = John
3 mechanisms that contribute to genetic variation:
1. Independent Assortment of Chromosomes 2. Crossing Over 3. Random Fertilization
What are the 3 ways meiosis is different than mitosis?
1. Prophase l - synapsis and crossing over 2. Metaphase l - pairs of homologous chromosomes line up on metaphase plate 3. Anaphase l - homologous pairs separate - sister chromatids still attached at centromere
Females must receive _______ copies of the gene, 1 on each X chromosome, to express the trait
2 - they can be carriers if heterozygous
What happens in Telophase l & Cytokinesis?
2 haploid cells; each chromosome = 2 sister chromatids
What are autosomes?
22 pairs of chromosomes that do not determine sex
Packet - A cell has 12 chromosomes (2n = 12). If this cell went through Meiosis, how many cells would there be: How many chromosomes in each?
4 cells each with 6 chromosomes
What is the result of meiosis?
4 daughter cells, each with half as many chromosomes as parent cell
Packet - Here is the percent recombination data for a set of four genes on the same chromosome. What is the most likely order of the genes? A - B 2% A - C 23% A - D 45% B - C 21% C - D 22%
A B C D
AP Classroom - What is the purpose of a chi-square goodness-of-fit test?
A chi-square goodness-of-fit test evaluates numerical data from 2 groups to determine if the observed results are significantly varied from the expected results
AP Classroom - What are a monohybrid cross and a dihybrid cross?
A monohybrid cross examines the inheritance of 1 trait and a dihybrid cross examines the inheritance of 2 traits
AP Classroom - What is crossing over, and how does it increase genetic diversity?
Crossing over in prophase l occurs when nonsister chromatids exchange segments. This results in recombinant chromosomes.
What are alleles?
Alternate version of genes that cause variations in inherited characteristics among offspring
What are somatic cells?
Body cells - 2n = 46 chromosomes
AP Classroom - What effect does chromosomal inheritance have on genetic variation and human disorders?
Certain human genetic disorders can be attributed to chromosome ainherticat and can result in genetically varied offspring
AP Classroom - How can chromosomal inheritance show patterns of transmission of genes from parents to offspring?
Chromosomes are inherited as full units and passed from parents to offspring
What is a Punnett Square?
Device for predicting offspring from a cross
AP Classroom - What is the difference between diploid and haploid?
Diploid cells have pairs of chromosomes (a full set), one from each parent, and are represented by 2n. Haploid cells have a single set of chromosomes, represented by n.
AP Classroom - How does fertilization increase genetic diversity?
During sexual reproduction, any gamete from one parent can combine with any gamete form another parent, resulting in genetically different offspring. This increases the genetic diversity within a population of organisms.
AP Classroom - What effect do environmental conditions have on gene expression?
Environmental factors can influence how genes are expressed - this leads to phenotypic plasticity
What is the F1 generation?
F1 (first filial) generation - P offspring
What is the F2 generation?
F2 (second filial) generation - F1 offspring
Packet - There are trillions of times more possible genetic varieties of humans than than the number of people who have ever lived. Explain why genetic variety is so important to a species.
Genetic diversity allows populations to adapt to any change in the environment in a population with a lot of genetic variation, it is more likely that some organisms will have a variation that allows them to survive. They are more likely to survive to reproduce, passing that trait on to their offspring.
Packet - If your father passes away from Huntington's disease, but your mother does not have the disease, what is the chance that you have inherited Huntington's?
Huntington's is an autosomal dominant disease. If your father had the disease, he was likely heterozygous and therefore you have a 50% chance of inheriting it. If he was homozygous, it would be a 100% chance that you have the disease.
Packet - Hemophilia is a sex linked trait. Mary's father has hemophilia, but she does not. She marries a man who does not have hemophilia. What are the chances that she has a son with hemophilia? Make a punnett square to prove your answer!
If Mary's father has hemophilia, his X chromosome has the hemophilia gene, which he passed on to all his daughters (mary). Mary then is a carrier, and will pass her affected X fifty percent of the time. For her boys, this would be their only X, so they would have hemophilia. Overall the son has a 25% chance of having hemophilia
What are recombinants?
If different from parents
What are parental types?
If offspring look like parents
AP Classroom - How does inheritance determined by multiple genes differ from Mendelian inheritance?
Inheritance determined by multiple genes has a larger number of possible genotypes and a larger range of phenotypes possible compared to inheritance determined by a single gene. These traits do not segregate in Medielain patterns.
Packet - In your own words, explain how these facts can be used to support the theory that all life evolved from a common ancestor. Include: What traits must that common ancestor have had?
It is assumed that the most recent common ancestor to all life had traits which allowed it to be successful. These traits were passed on to the offspring of that ancestor, and their offspring, and theirs ... passing to all domains of life as they evolved. The most recent common ancestor to all organisms must have had DNA, RNA, ribosomes, and core metabolic pathways (example: glycolysis)
AP Classroom - What are linked genes?
Linked genes are genes located on the same chromosome that are typically inherited together
AP Classroom - What does map distance tell you about a pair of linked genes?
Map distance tells you how close together a pair of linked genes is. The smaller the map distance, the closer together the genes are on the chromosome and the more likely those genes will be inherited together.
AP Classroom - What happens in the series of steps that make up meiosis?
Meiosis involves 2 rounds of cell division. In meiosis l, pairs of chromosomes separate, resulting in 2 haploid cells containing only 1 of the double chromosomes from each pair. In meiosis ll, double chromosomes separate, resulting in 4 haploid cells, each with single chromosomes.
What are the overall steps of Meiosis?
Meiosis l - Interphase - Prophase l - Metaphase l - Anaphase l - Telophase l & Cytokinesis Meiosis ll - Prophase ll - Metaphase ll - Anaphase ll - Telophase ll
AP Classroom - What is Mendel's law of independent assortment?
Mendel's law of independent assortment states that genes are not linked
AP Classroom - What is Mendel's law of segregation?
Mendel's law of segregation states that alleles are segregated into separate gametes during meiosis
Packet - What causes "variety" in our mitochondrial DNA?
Mitochondrial DNA is subject to mutations, just like nuclear DNA
AP Classroom - What similarities and differences are there between mitosis and meiosis?
Mitosis and meiosis are similar in the overall process (PMAT) of genetic information is passed onto daughter cells. However, mitosis produces 2 genetically identical cells and meiosis produces 4 haploid genetically varied cells.
AP Classroom - How does non-nuclear inheritance differ from Mendelian inheritance?
Non-nuclear inheritance seen in chloroplasts and mitochondria is maternally inherited. These traits do not segregate in Mendelian patterns.
AP Classroom - What is nondisjunction and how does it contribute to genetic variation?
Nondisjunction is the failure of chromosomes to fully separate during the formation of gametes - this results in too many or too few chromosomes in the sex cells
What is the P generation?
P (parental) generation - true breeding plants
AP Classroom - How can human genetic disorders be based on chromosomal inheritance?
Patterns of inheritance of traits, diseases, or disorders can be analyzed to determine how chromosomes were inherited
AP Classroom - What is a pedigree and how do the patterns show types of inheritance?
Pedigrees show inheritance patterns within families and can be used to predict inheritance of traits in subsequent generations
AP Classroom - What is phenotypic plasticity?
Phenotypic plasticity is the ability of one genotype to produce more than one phenotype
A man who is heterozygous with type A blood marries a woman who is homozygous with type B blood. What possible blood types with their children have?
Possible blood types = AB or B
AP Classroom - Why are these processes considered fundamental for continuity of life?
Processes like cellular respiration and transmission of genetic information allow life to continue through generations
AP Classroom - When does random assortment of chromosomes in meiosis increase genetic diversity?
Random assortment of chromosomes in metaphase l can result in different combinations of chromosomes in gametes.
AP Classroom - How does fertilization in sexually reproducing organisms lead to genetic variation?
Random fertilization leads to genetic variation in offspring of sexually reproducing organisms
AP Classroom - How do sex-linked traits differ from Mendelian traits?
Sex-linked traits differ from Mendelian triats because each parent does not contribute sex-linked alleles to every biological offspring, like with Mendelian inheritance; biological sex will determine which sex-linked alleles are inherited.
AP Classroom - How do conserved processes support the concept of common ancestry?
Shared and conserved processes support the concept of common ancestry because fundamental features link organisms by lines of descent
AP Classroom - What are autosomal dominant traits?
Show a pattern of affected offspring with affected parents
AP Classroom - What are autosomal recessive traits?
Show a pattern of affected offspring with unaffected parents
Packet - Your mother passes away from sickle cell anemia, but your Father is normal. What is the chance that you have inherited the disease?
Sickle Cell is an autosomal recessive trait. Your mother would have been homozygous recessive. If your father is normal, homozygous dominant then you would be a carrier, but not have the disease.
AP Classroom - How does independent assortment result in genetic variation?
The assortment of genes independently into gametes provides more possible gene combinations when fertilization occurs
How temperature often influence the color of animal fur
The genes for fur color in Siamese Cats produce a dark fur pigment in cold areas of the animal (feet, ears, face and tail) & a light pigment in the remaining warm areas
Packet - Short stems are recessive to long stems, and white is recessive to purple.. You cross a white short plant with a heterozygous purple long plant, The offspring are: 445 white short 18 white long 15 purple short 450 purple long Which of Mendel's Laws is being broken? Why is this happening? What is the percent recombination of the above cross? Show your work!
The law of Independent Assortment is being broken. The offspring should be in a 1:1:1:1 ratio, but they are not. This means these 2 traits must be on the same chromosome, and only when crossing over happens will the alleles separate. Frequency is the number of recombination offspring (18+15) divided by total number of offspring (445+18+15+450) = 33 / 928 = 0.036 = 3.56%
AP Classroom - What is the purpose of meiosis?
The purpose of meiosis is to produce haploid gametes.
AP Classroom - How can the same genotype result in multiple phenotypes?
The same genotype can result in multiple phenotypes due to changes in environmental conditions
AP Classroom - How does the law of segregation account for genetic variation?
The segregation of parental alleles into gametes provides opportunity for more varied combinations of allele when fertilization occurs
AP Classroom - What steps are necessary to perform a chi-square goodness-of-fit test?
The steps required of a chi-square goodness-of-fit test include establishing a question and hypotheses, determining the observed and expected values, calculating the chi-square value, identifying the critical value, and drawing a conclusion determining whether the null hypothesis t should be rejected or if the data fail to reject the null
Packet - Why is it rare to find a girl that is color blind?
The trait for color blindness is on the X chromosome. Males have just one X, so if it has the gene they will have the trait. Females have two X chromosomes, so they are more likely to be heterozygous and not have the trait.
AP Classroom - How can the laws of probability be applied to genetic crosses?
Understanding Mendel's laws allows for the application of mathematical calculations and laws of probability to predict genetic events
Packet - A particular mutation in a species of plant leads to variegation in its leaves (part of each leaf is white, while part is green).A plant breeder takes pollen from a green plant and pollinates a variegated plant. All resulting offspring are variegated. The breeder then takes pollen from a variegated plant and pollinates a green plant. All resulting offspring are green. What is going on?
Variegation is due to a gene found in the chloroplast. Like mitochondria, chloroplasts are passed directly from mother to offspring. Therefore females variegated plants will always have variegated offspring, while male variegated plants will not pass on this trait.
AP Classroom - How can we use visual representations to analyze changes or disruptions in chromosomal inheritance?
Visual representations such as pedigrees can be used to help us predict the causes or effects of changes in chromosomal inheritance from parents to offspring
Packet - Two yellow squash will always have yellow offspring. White squash will sometimes have white offspring, but sometimes yellow. Which trait is dominant?
White is dominant. Yellow plants (recessive) are homozygous, so they would always have homozygous recessive yellow offspring. White plants could be homozygous or heterozygous. 2 heterozygous yellow squash could have white offspring.
Packet - White flower color is recessive to purple flower color in pea plants. A white pea plant is crossed with a purple pea plant, yielding 554 white offspring and 568 purple offspring. What are the genotypes of each parent?
White is recessive, so it must be homozygous recessive. Purple is dominant, the purple plant could be homozygous dominant or heterozygous. If the purple parent were homozygous, all of the offspring would be purple. Since they were half purple and half white, the purple plant must be heterozygous.
What are sex chromosomes?
X and Y - Females = X - Males = Y
AP Classroom - What is a trait?
a genetically determined characteristic of an organism - genes determine traits
What is a karyotype?
a picture of an organism's complete set of chromosomes
AP Classroom - What is an allele?
a specific variation of a gene
AP Classroom - What is a gene?
a unit of heredity coding for a trait - can be transferred from one generation to the nex
What is meiosis?
cell division that reduces number of chromosomes (2n --> n), creates gamete
Offspring acquire genes from parents by inheriting ____________
chromosomes
What is nondisjunction?
chromosomes fail to separate properly in Meiosis l and Meiosis ll - result is gametes with extra or missing chromosomes
What happens in Metaphase ll?
chromosomes line up
What happens in interphase?
chromosomes replicate
What is fertilization?
combine gametes (sperm + egg)
If 2 alleles are different, the ___________ allele will be fully expressed; the ___________ allele will have no noticeable effect on offspring appearance
dominant - recessive
What is a Phenotypic Ratio?
dominant or recessive
In a double heterozygous organism (AaBb), this results in the formation of gametes with ________ frequency
equal or 25%
When genes are ____________________ or ____________________ the assort independently
far on the same chromosome or on separate chromosomes
_____________ and __________ alternate in sexual life cycles
fertilization - meiosis
2 very close-together genes will have ________ recombination events and be __________ linked
few - tightly
What is a Genotypic Ratio?
homozygous dominant: heterozygous: homozygous recessive
2 genes that are further apart will have ______ recombination events and be __________ linked
more - less tightly
What are gametes?
n = 23 - 22 autosomes + 1 chromosome - egg: 22 + X - sperm: 22 + Y
Each pair of homologous chromosomes includes ____ chromosome from each parent
one
For each character, every organisms inherits _____ allele from each parent
one
AP Classroom - What is a alternative hypothesis?
one of many possible hypotheses that states observed results are due to a nonrandom cause
What is oogenesis?
process by which ova are produced by the female - 3 polar bodies and 1 ovum are createdWh
What is spermatogenesis?
process by which sperm are produced by the male - 4 spermatids are created
What is genetic recombination?
production of offspring with combination of traits different from either parent
Is Widow's Peak dominant or recessive?
recessive
What are life cycles?
reproductive history of organism: from conception --> production of own offspring
What are genes?
segments of DNA that code for basic units of heredity
What happens in Anaphase ll?
sister chromatids separate
AP Classroom - What is a null hypothesis?
states there is no relationship or no difference between 2 groups of data in an investigation
What happens in Metaphase l?
tetrads line up
What is the Law of Segregation?
the 2 alleles for each character separate during gamete formation
AP Classroom - What is a genotype?
the combination of inherited alleles
AP Classroom - What is a phenotype?
the physical result or expression of the genotype
In meiosis cells divide _______
twice
