AP Biology Unit 5 Heredity Vocab

Vocabulary

Meiosis

This divides one diploid cell (cell with two sets of chromosomes) to haploid cells (single set of chromosomes). In two rounds, it creates 4 haploid cells.

Round 1: first round of cell division, homologous pairs separate.

Round 2: second round of cell division, sister chromatids separate, resulting in 4 haploid cells each with a single chromosome.

Heterozygous

This is having two different alleles of a particular gene or genes.

Homozygous

This refers to having inherited the same versions (alleles) of a genomic marker from each biological parent. They could both be dominant or both be recessive.

Maternal Inheritance

This refers to the transmission of the mitochondrial genome from a mother to all her children, with no paternal mtDNA contribution. During fertilization, a human sperm cell, with its few mitochondria, does not contribute significantly to the zygote.

Conditions caused by variants in mitochondrial DNA can affect both males and females, but fathers do not pass these disorders on to offpsring.

Gamete

This is a reproductive cell of an animal or plant. In animals, female BLANKs are called ova or egg cells, and male BLANKs are called sperm. Ova and sperm are haploid cells, with each cell carrying only one copy of each chromosome.

Prophase 1

Part of round one of Meisosis,

• nuclear envelope begins to disappear

• Fibers begin to form

• DNA coils into visible duplicated (or double) chromosomes made up of sister chromatids

• Double chromosomes pair up based on size, shape, centromere location, genetic information

• While paired, chromatids exchange genetic info with chromatids from the other chromosome (non-sister chromatids exchange genetic info)

Metaphase 1

Part of Meiosis 1:

• Double chromosomes remain in pairs

• fibers align pairs across the center of the cell

Anaphase 1

Part of meiosis 1

• Fibers separate chromosome pairs

• each double chromosome, from the pair, migrates to opposite sides of the cell

Telophase 1

Part of meiosis 1

• Nuclear envelope reappears and establishes two separate nuclei

• Each nucleus contains only one double chromosome from each pair

  • Nucleus only contains half of the total information the parent nucleus contained

• Chromosomes will begin to uncoil

Cytokinesis will separate the cell into two daughter cells.

Meiosis II

This is the second round, now in anaphase 2 the fibers separate sister chromatids and chromatids (single chromosome) migrate to opposite sides.

Crossing Over

This occurs during prophase I of Meiosis I.

No sister chromatids of double homologous chromosomes (carry info for the same genes, one from each parent) exchange segment.

Results in recombinant chromatids. It increases genetic diversity among gametes.

Random Assortment

The order of homologous pairs during metaphase I affects which chromosomes end up in each gamete.

Different combinations of chromosomes in each gamete increase genetic diversity.

Fertilization of gametes

This is another way to increase genetic variation. It occurs when one gamete from each parent fuse together to form a diploid offspring. It is random in that any gamete can contribute to the diploid nature of genomes in offspring; increases potential for genetic diversity.

Common Ancestry

According to modern evolutionary biology, all living beings could be descendants of a unique ancestor commonly referred to as the last universal common ancestor of all life on Earth.

Evidence of this includes:

All organisms have:

• DNA

• Ribosomes

• core metabolic processes (like cellular respiration, aerobic or anaerobic), glycolisis.

Genotype

This is the combination of inherited alleles.

Phenotype

This is the physical result or expression of the genotype.

Law of segregation

When chromosomes are separated into daughter cells during meiosis, the alleles for each trait are also separated. Separation of alleles allows for genetic variation among gametes.

Law of Independent Assortment

Two or more genes assort independently of each other. One trait is not automatically inherited with another trait. Alleles for separate traits can be packaged in every possible combination into gametes. This leads to a ratio of 1:1:1:1

Autosomal dominant traits

These are traits on non-sex cells that show a pattern of affected offspring with affected parents in a pedigree chart.

Autosomal recessive traits

These are traits on non-sex cells that show a pattern of affected offspring with unaffected parents in a pedigree chart.

Degrees of Freedom

This is equal to the number of distinct possible outcomes minus one.

Chi-square Value

This is equal to [the sum of the (observed - expected)² / expected ].

If this value is less than the critical value, there is no relationship between the traits, and they assort independently of each other. (“fail to reject null hypothesis”)

If this value is greater than the critical value, there is a relationship between the two traits.

Linked Genes

These are genes that are adjacent and close to one another on the same chromosome and that are inherited together. They do not follow predicted ratios associated with Mendel’s laws and can be identified by quantitative analysis. They are typically inherited together and are less likely to be separated during crossing over in meiosis (they have a recombination frequency of less than 50%).

Sex-linked traits

These are traits that are determined by genes located on sex chromosomes. Sex chromosomes determine biological sex in animals and are nonhomologous. They do not follow predicted ratios associated with Mendel’s laws and can be identified by quantitative analysis.

If its a BLANK recessive pedigree:

• there is a pattern of affected offspring with unaffected parents

• biological males are more likely to be affected than females

• sometimes female carriers are shown as half-shaded circles

Map distance

This tells you how close together a pair of linked genes is. It is determined by how frequently a pair of genes participates in a single crossover event. Linked genes have a recombination frequency of less than 50%.

The percent of recombination is equal to the BLANK, so 28% recombination is 28 map units.

Phenotypic Plasticity

Environmental conditions can change the expression of a gene. This is the ability of one genotype to produce more than one phenotype. Phenotypic diversity can be due to environmental factors and not necessarily due to genetic diversity.

ex. in hydrangea plants, the color of the flower is determined by the pH of the soil.

ex. the number of stomates in a plant can be determined by the amount of CO2 in the atmosphere.

Nondisjunction

This 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.

Triple X Syndrome

This is usually caused by a malformation of egg or sperm cells.

• Nondisjunction resulting in reproductive cells with more than chromosomes

• Resulting in offspring with more than 2 sex chromosomes.

Huntington’s Disease

This is a progressive and eventually fatal neurological disorder. It is caused by a single defective gene on chromosome 4. Inheritance is autosomal dominant, meaning that if you inherit the affected chromosome from a parent, you will get the disease.

Codominance

This refers to a type of inheritance in which two versions (alleles) of the same gene are expressed separately to yield different traits in an individual. This creates a ratio of 1:2:1 when they have 1 heterzygous trait and a ratio of 6:3:32:1:1 when they have 2 heterozygous traits.

Incomplete Dominance

This is the genetic phenomenon in which the distinct gene products from the two codominant alleles in a heterozygote blend to form a phenotype intermediate between those of the two homozygotes. This creates a ratio of 1:2:1 when they have 1 heterzygous trait and a ratio of 6:3:32:1:1 when they have 2 heterozygous traits.

Complete Dominance

This refers to a situation where one allele in a gene pair completely masks the effect of the other allele, So homozygous dominant and heterozygous will both have the dominant phenotype. It creates a ratio of 3:1 when they are heterozygous for one trait, and a ratio of 9:3:3:1 when they are heterozygous for 2 traits.