Genetics

• The two major groups of specialized cells in your body are _______ and ________.

• Somatic cells and germ cells

• ______ cells, also called body cells, make up most of your body tissues and organs.

• Somatic cells

• DNA is passed on to offspring by ____ ___.

• Germ cells

• Gametes are ____ cells.

• sex

• Each species has a characteristic number of ______ per cell.

• chromosomes

• Chromosome number does not seem to be related to the _______ of an organism.

• complexity

• Humans have ___ chromosomes in ___ pairs.

• 46, 23

• Humans receive 23 chromosomes from the _____ and 23 from the _____.

• Mother, father

• In humans, each pair of chromosomes is referred to as a ________ ____.

• Homologous pair

• Homologous means…….

• Having the same structure

• A number has been assigned to each homologous pair, ordered from _____ to _____.

• Largest to smallest

• Chromosome pairs 1-22 make up your ______.

• autosomes

• These chromosomes are not directly related to the sex of an organism.

• autosomes (1-22)

• The two human sex chromosomes are __ and __.

• x and y

• An organism with two X chromosomes is _____.

• female

• An organism with one X chromosome and one Y chromosome is ____.

• male

• X and Y chromosomes are not _______.

• homologous

• The ____ chromosome is larger and contains numerous genes.

• X

• ______ _______ involves the fusion of two gametes that results in offspring that are a genetic mixture of both parents.

• Sexual reproduction

• The actual fusion of an egg and sperm cell is called _______.

• fertilization

• When fertilization occurs, the nuclei of the egg and sperm cell fuse to form one _____.

• nucleus

• Egg and sperm cells only have half the usual number of ______.

• chromosomes

• Body cells are ____, meaning that a cell has two copies of each chromosome.

• diploid

• Gamete cells are _____, meaning that one cell has one copy of each chromosome.

• haploid

• The sex of an individual is determined by the _____.

• Male (for humans)

• Increasing the number of sets of chromosomes can give rise to a new _____.

• species

• 4 copies of each chromosome.

• A condition called tetraploidy

• Germ cells in human reproductive organs undergo _____ to form gametes.

• meiosis

• ______ is a form of nuclear division that divides a diploid cell into haploid cells.

• meiosis

• ______ is a type of cell division that occurs in body cells.

• Mitosis

• What are some of the differences between mitosis an meiosis?

• In mitosis, DNA is copied once and divided once. In meiosis, DNA is copied once but divided twice.

• In mitosis, daughter cells are genetically identical to the parent cell. Meiosis makes genetically unique haploid cells from a diploid cell.

• Mitosis is used for growth, development, and repair. Takes place throughout life. Meiosis, however, takes place only at certain times.

• Mitosis is involved in asexual reproduction, meiosis is involved in sexual reproduction.

• Where are germ cells located in the human body?

• Ovaries and testes• What is the difference between an autosome

and a sex chromosome?• Autosomes, chromosomes 1-22, are not

directly related to the sex of an organism.

• Is the cell that results from fertilization a haploid or diploid cell? Explain.

• Each cell has only one copy of each chromosome. It takes the combination of an egg and sperm cell to make the 46 human chromosomes…..so haploid.

• Does meiosis or mitosis occur more frequently in your body?

• Mitosis, it is responsible for growth, development, and repair.

• Meiosis is responsible for reproduction.

• _______ is a form of nuclear division that creates four haploid cells from one diploid cell.

• Meiosis• Meiosis _______ chromosome number and

creates genetic _________.• reduces,diversity

• Each half of a duplicated chromosome is called a ________.

• Chromatid• ______ ______ are the duplicated

chromosomes that remain attached by the centromere.

• Sister Chromatids

• ______ ______ are divided during meiosis I. ____ ______ are not divided until meiosis II.• Homologous chromosomes• Sister chromatids

• Before meiosis begins, _______ has already been copied.

• DNA• What are the 4 stages of meiosis I?• Prophase I• Metaphase I• Anaphase I• Telophase I

Identify the phase in meiosis I.

• The nuclear membrane breaks down centrosomes and centioles move to opposite sides of the cell. Spindle fibers assemble Homologous chromosomes pair up

• Prophase I

Identify the phase in Meiosis I

• Homologous chromosome pairs are randomly lined up along the middle of the cell by spindle fibers.

• Metaphase I

Identify the phase in Meiosis I

• Paired homologous chromosomes separate and move to opposite sides of the cell.

• Anaphase I

Identify the phase in Meiosis I

• The nuclear membrane forms, the spindle fibers disassemble, and the cell undergoes cytokinesis.

• Telophase I

Identify the phase in Meiosis II

• The nuclear membrane breaks down, centrosomes and centrioles move to opposite sides of the cell, spindle fibers assemble.

• Prophase II

Identify the phase in Meiosis II

• Spindle fibers align the 23 chromosomes at the cell equator

• Metaphase II

Identify the phase in Meiosis II

• The sister chromatids are pulled apart from each other and move to opposite sides of the cell.

• Anaphase II

Identify the phase of Meiosis II

• Nuclear membranes form around each set of chromosomes at opposite ends of the cell, spindle fibers break apart, the cell undergoes cytokinesis, and four haploid cells are produced.

• Telophase II

• What is the major difference between Metaphase I and Metaphase II?

• In metaphase I, pairs of homologous chromosomes line up at the equator. In metaphase II, the chromosomes are not paired.

• What is the major difference between Anaphase I and Anaphase II?

• Sister chromatids remain together in Anaphase I but separate in Anaphase II.

• ___________ is the production of gametes.• Gametogenesis

• The sperm cell’s main contribution to an embryo is ____________.

• DNA

• Distinguishing characteristics that are inherited, such as eye color, leaf shape, and tail length.

• Traits

• The study of biological inheritance patterns and variation in organisms.

• Genetics

• The groundwork for genetics was laid in the middle 1800’s by an Austrian monk named ________ ________.

• Gregor Mendel

• What three key choices did Mendel make in his experiments that helped him develop his laws of inheritance?

1. Control over breeding2. Use of purebred plants3. Observation of “either-or” traits that

appeared in only two alternate forms

• Why did Mendel choose pea plants for his experiments?

• They reproduce quickly and it is easy to control fertilization

• Genetic Uniformity. The offspring inherit all of the parent organisms’ characteristics.

• purebred

• What seven traits for pea plants did Mendel observe?

• Pea shape• Pea color• Pod shape• Pod color• Plant height• Flower color• Flower position

• In genetics, the mating of two organisms is called a …

• cross

• Mendel called the very first purebred generation of pea plants the ________, or ________ generation.

• Parental or P

• Mendel called the offspring of the parental generation the ______ ______ generation.

• First filial

• Mendel called the generation after the first filial generation the ________ generation.

• F₂

• What happened with Mendel’s F₂ generation?• Plants were produced with both purple and

white flowers, the entire F₁ generation produced purple flowers, the trait for white flowers had not disappeared; it had been masked.

• What pattern did Mendel notice in the F2 generation?

• Similar ratios were noticeable

• What conclusions did Mendel draw from his observations?

• Traits are inherited as discrete units.• Organisms inherit two copies of each gene,

one from each parent.• Organisms donate only one copy of each gene

in their gametes.

• A piece of DNA that provides a set of instructions to a cell to make a certain protein.

• Gene

• Any of the alternative forms of a gene that may occur at a specific locus.

• Allele

• Your cells have ______ alleles for each gene.• Two

• A term used to describe two of the same alleles at a specific locus.

• Homozygous

• A term used to describe two different alleles at a specific locus.

• Heterozygous

• All of an organism’s genetic material.• Genome

• This term refers to the genetic makeup of a specific set of genes.

• Genotype

• The physical characteristics, or traits, of an individual make up its ________.

• Phenotype

• The allele that is expressed when two different alleles are present.

• Dominant

• The allele that is expressed when two copies are present.

• Recessive

• A grid system for predicting all possible genotypes resulting from a cross.

• Punnett Square

• What do the letters on the axes of the punnett square represent?

• The condition of alleles from each parent.

• A cross that examines the inheritance of only one specific trait.

• Monohybrid crosses

• FF• Homozygous Dominant

• ff• Homozygous Recessive

• Ff• Heterogygous Parent

• A cross between an organism with an unknown genotype and an organism with the recessive phenotype.

• Test-cross

• From an FF x ff cross, what percent of offspring would have purple flowers? (Purple being dominant)

• 100% F F

f Ff Ff

f Ff Ff

• From an Ff x Ff cross, what percent of offspring would have purple flowers? (purple being dominant)

• 75% F f

F FF Ff

f Ff Ff

• From an ff x Ff cross, what percent of offspring would have purple flowers? (purple being dominant)

• 50% f f

F Ff Ff

f ff ff

• Crosses that examine the inheritance of two different traits.

• Dihybrid crosses

• Allele pairs separate independently of each other during gamete formation, or meiosis. Different traits appear to be inherited separately.

• The Law of Independent Assortment, The Second Law of Genetics

• The likelihood that a particular event will happen

• probability

• Number of ways a specific even can occur Number of total possible outcomes

• Probability

• Why does the expected genotypic ratio often differ from the expected phenotypic ratio resulting from a monohybrid cross?

• Multiple genotypes can cause the same phenotype. The homozygous dominant genotype and the heterozygous genotype yield the same phenotype in simple dominant-recessive cases

• What is the major advantage of sexual reproduction?

• It gives rise to a great deal of genetic variation

• Genetic variation within species results largely from

• The independent assortment of chromosomes during meiosis and the random fertilization of gametes

• The exchange of chromosome segments between homologous chromosomes during prophase-I of meiosis-I

• Crossing over

• Any mixing of parental alleles• recombination

• Genes located close together tend to be inherited together.

• Genetic linkage

• How does crossing over contribute to genetic diversity?

• Crossing over makes new combinations of maternal and paternal genes

• The word meiosis comes from a Greek word meaning “to diminish”, or make less. How does this word’s origin relate to its meaning?

• Meiosis is a reductive process that diminishes, or reduces, the amount of DNA. It begins with a diploid cell and ends with haploid cells.

• A fruit fly has diploid cells with 8 chromosomes. Explain how many chromosomes are in its haploid gametes

• 4 chromosomes, because meiosis results in haploid gamete cells, with only one set of chromosomes.

• Many human genetic disorders are caused by _______ genes.

• autosomal

• For a genetic disorder to be caused by a recessive allele, ____ _______ must be present for a person to have the disorder.

• Two copies

• An individual who does not show disease symptoms but can pass on the disease causing allele to offspring.

• Carrier

• Genes located on the sex chromosome• Sex-linked genes

• Males (XY) have only one copy of each type of sex chromosome. Because of this, males express ____ alleles on both chromosomes, even if all alleles are _______.

• All, recessive

• In female mammals, this is when one of the two X chromosomes is randomly turned off.

• X-chromosome inactivation

• Why are males more likely than females to have sex-linked genetic disorders?

• All sex-linked genes, even recessive ones, are expressed in males.

• How are autosomal traits, including recessive genetic disorders, related to Mendel’s observation of heredity?

• Two copies of autosomal genes affect phenotype, as observed in all of Mendel’s crosses

• How might a scientist determine whether a trait is sex-linked by observing the offspring of several genetic crosses?

• If more males than females have a particular phenotype, the trait is probably sex-linked

• Why are female calico cats white, black, and orange, while male calico cats are white and orange or white and black?

• Males cats have only one X chromosome.

• Does dominance mean that one allele defeats the other?

• No. The dominant allele usually codes for a specific protein. The recessive allele codes for a variation of the protein that has little or no effect.

• Neither allele is completely dominant or completely recessive.

• Incomplete dominance

• What are two examples of incomplete dominance?

• The 4 o’clock plant. When plants that are homozygous for red flowers are crossed with plants that are homozygous for white flowers, the offspring have pink flowers.

• The color of betta fish. When a green betta fish is crossed with a steel blue fish, the result is a royal blue betta fish.

• The expression of both alleles of a gene. Neither allele is dominant or recessive.

• codominance

• Provide an example of codominance.• A flower that has red and white splotches. The

human ABO blood type.

• Traits produced by two or more genes.• polygenic

• A lack of pigment in skin• Albinism

• In what ways may environment interact with genotype?

• For sea turtles, eggs that mature in warmer temperature develop into females. Cooler temperatures result in males.

• Amount of available nutrients during developmental stages of life may affect size

• What two scientists first described gene linkage?

• William Bateson and RC Punnett

• Traits that are inherited together.• Linked traits or gene linkage