Law of Independent Assortment Quiz & Flashcards

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Questions and Answers

What are autosomes?

The other 22 pairs of chromosomes that are the same size and shape.

What are sex-linked characteristics?

Characteristics that are determined by genes that occur on the X chromosome.

What is a carrier?

A female who has an allele for an abnormal condition but does not show it.

How is the presence of haemophilia determined in males and females?

In females, XNXN represents normal blood clotting, XNXn represents carrier status, and XnXn represents haemophilia. In males, XNY- represents normal blood clotting, XnY- represents haemophilia. Signup and view all the answers

What is the definition of a dominant allele?

The dominant allele is the allele that is always expressed if it is present. Signup and view all the answers

What is the definition of a recessive allele?

The recessive allele is the allele whose expression is masked by the dominant allele. Signup and view all the answers

What is the Law of Segregation according to Mendel's First Law?

The Law of Segregation states that each characteristic is governed by a pair of factors (genes) that separate at gamete formation, and each gamete only receives one of each pair of factors. Signup and view all the answers

What is the definition of phenotype?

Phenotype is the physical expression of the genotype or genotype plus environment. Signup and view all the answers

What is the phenotype ratio of the progeny when a heterozygous plant with round seeds is crossed with a pea plant that produces wrinkled seeds?

1 (50%) round : 1 (50%) wrinkled Signup and view all the answers

What is the phenotype ratio of the progeny when a heterozygous tall pea plant is crossed with a heterozygous tall pea plant?

3 tall : 1 dwarf Signup and view all the answers

What is the phenotype ratio of the progeny when a parent with a red coat and a parent with a white coat produce offspring with a mottle color called roan?

co-dominance or incomplete dominance Signup and view all the answers

What is the purpose of adding sodium chloride (salt) to the washing up liquid in distilled water when isolating DNA from plant tissue?

The purpose of adding sodium chloride (salt) is to help break down the proteins around the DNA. Signup and view all the answers

What is the role of RNA polymerase in transcription?

RNA polymerase is responsible for forming the mRNA strand by copying the information from the DNA. Signup and view all the answers

What is the role of tRNA in protein synthesis?

tRNA brings specific amino acids to the ribosome based on the codons on the mRNA, allowing for the assembly of the protein. Signup and view all the answers

What is the difference between dominant and recessive gene alleles?

Dominant gene alleles are stronger and their characteristics are expressed in the organism, while recessive gene alleles are weaker and their characteristics are only expressed when there are no dominant alleles present. Signup and view all the answers

What is a species and why is fertility important in defining a species?

A species is a group of organisms that can interbreed and produce fertile offspring. Fertility is important in defining a species because occasionally two different, but closely related species can interbreed and produce an infertile hybrid. Signup and view all the answers

What is heredity and how does it relate to gene expression?

Heredity is the passing on of characteristics from one generation to the next by genes. Gene expression is the process by which the information from a gene is used to produce a feature or a protein. Heredity and gene expression are related because genes control traits and characteristics that are passed on through heredity. Signup and view all the answers

What is an allele and how does it relate to chromosome structure?

An allele is one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome. Alleles are either dominant or recessive. Chromosome structure includes specific positions on a chromosome called loci, where genes and their alleles are located. Signup and view all the answers

What is the structure of DNA?

DNA is a polymer with thousands of repeating units arranged in a double helix structure. The sides of the ladder consist of alternating deoxyribose sugar and phosphate groups, while the rungs consist of complementary bases held together by hydrogen bonds. The four bases are adenine (A), thymine (T), guanine (G), and cytosine (C). Signup and view all the answers

What is the process of DNA replication?

DNA replication occurs in the nucleus during interphase of mitosis and meiosis. The double helix untwists and unzips, and free nucleotides enter the nucleus from the cytoplasm. New nucleotides form a new chain, using each strand as a template. Each new DNA molecule is half new and half old, and identical to the original and each other. The new DNA molecules rewind to form a double helix. Signup and view all the answers

What are the differences between RNA and DNA?

RNA contains the sugar ribose instead of deoxyribose, and the base thymine found in DNA is replaced by uracil in RNA. RNA is single stranded while DNA is double stranded. Signup and view all the answers

What are the three types of RNA and their functions?

The three types of RNA are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). mRNA carries information from the DNA in the nucleus to the ribosomes in the cytoplasm for protein synthesis. rRNA is a major part of the structure of ribosomes. tRNA collects and brings specific amino acids to the ribosomes for protein assembly. Signup and view all the answers

What is Mendel's second law and how does it relate to gamete formation?

Mendel's second law states that during gamete formation, any member of a pair of factors has an equal chance of entering a gamete with either member of any other pair of factors. This means that the inheritance of one trait is independent of the inheritance of another trait. Signup and view all the answers

Explain the phenotype and genotype ratios in the first filial generation (F1) resulting from the cross between the heterozygous tall peas with red flowers and the homozygous recessive dwarf white flowered peas.

In the first filial generation (F1), the phenotype ratio is 1 tall red : 1 tall white : 1 dwarf red : 1 dwarf white, and the genotype ratio is TtRr : Ttrr : ttRr : ttrr. Signup and view all the answers

What is the phenotype ratio in the second filial generation (F2) resulting from a dihybrid cross between a homozygous dominant pea plant and a homozygous recessive pea plant?

The phenotype ratio in the second filial generation (F2) is 9 tall red : 3 tall white : 3 dwarf red : 1 dwarf white. Signup and view all the answers

What is the significance of crossing over in the production of non-parental phenotypes in offspring?

Crossing over is the swapping of sections of homologous chromosomes during meiosis. It can lead to the production of non-parental phenotypes in offspring by creating new combinations of alleles on the chromosomes. Signup and view all the answers

Study Notes

Species and Variation

A species is a group of organisms that can interbreed and produce fertile offspring.
Fertility is a critical aspect, as two different but closely related species can interbreed and produce an infertile hybrid (e.g., mule, liger, cama, zonkey).
Variation refers to the differences between individuals of a particular species, including structural (e.g., height, weight, color), behavioral (e.g., aggressiveness), and other differences.

Heredity and Gene Expression

Heredity is the passing on of characteristics from one generation to the next by genes.
A gene is a length of DNA on a chromosome that codes for a protein or controls the development of a characteristic.
Gene expression is the process by which the information from a gene is used to produce a feature or a protein.
Dominant and recessive alleles can influence the expression of a gene.

Chromosome Structure

A chromosome is an organized length of DNA and proteins called histones.
Each gene has a specific position on a chromosome called the locus.
Alleles are different options for a gene, and they can be either dominant or recessive.
Chromosomes are composed of two strands called chromatids held together by a centromere.

DNA Structure

James Watson and Francis Crick discovered the molecular structure of DNA in 1951.
DNA is a polymer with thousands of repeating units.
The basic shape of DNA is a double helix.
The sides of the ladder consist of alternating deoxyribose sugar and phosphate groups.
The rungs consist of complementary bases (A, T, G, and C) held together by hydrogen bonds.
Adenine only pairs with Thymine, and Guanine only pairs with Cytosine.

DNA Replication

DNA replication occurs in the nucleus during interphase of mitosis and meiosis.
Energy (ATP) and the enzyme DNA polymerase are needed for DNA replication.
The process involves:
- The double helix opens and untwists.
- Free nucleotides enter the nucleus from the cytoplasm.
- New nucleotides form a new chain.
- Each strand acts as a template to make the opposite strand from complementary nucleotides.
- Each new DNA molecule is half new and half old, identical to the original, and each other.

RNA Structure

RNA contains the sugar ribose instead of deoxyribose.
The base Thymine found in DNA is replaced by Uracil in RNA.
RNA is single-stranded, while DNA is double-stranded.
There are three types of RNA:
- Messenger RNA (mRNA): carries information from DNA to ribosomes.
- Ribosomal RNA (rRNA): major part of the structure of ribosomes.
- Transfer RNA (tRNA): collects and brings specific amino acids to ribosomes.

DNA Profiling

DNA profiling is a method of making a unique pattern of bands from an individual's DNA.
The process involves:
- Extracting DNA from cells.
- DNA amplification using the polymerase chain reaction (PCR).
- Cutting the DNA using restriction enzymes.
- Gel electrophoresis: separating the fragments based on size.
- Transferring the DNA to a nylon membrane.
- Attaching radioactive pieces of DNA to make the fragments visible.

Genetic Screening

Genetic screening is checking for the presence or absence of a particular allele or gene.
The process involves:
- Adding a length of DNA with the same base sequence as the allele or gene.
- If the marker sticks to the DNA, it shows the gene is present.
- This can be used to check for genes associated with inheritable diseases.

Protein Synthesis

Protein synthesis is the process of building proteins out of their building blocks (amino acids).
The process involves:
- Genes (information store): the nucleus stores the information needed to produce the protein.
- Transcription (copying the information): DNA is unzipped, and an mRNA strand is formed.
- Movement of mRNA: the mRNA moves out of the nucleus into the cytoplasm.
- Translation (making the protein): the ribosomes attach to the mRNA, and tRNA brings amino acids to the ribosomes.

Genetic Inheritance

Gregor Mendel is considered the father of modern genetics.
Mendel's concepts:
- Each characteristic is controlled by a pair of factors (genes).
- There are two options for a characteristic, called alleles.
- Normally, one option is stronger than the other, and the strongest one is said to be dominant.
- The law of segregation states that each characteristic is governed by a pair of factors.
Types of crosses:
- Monohybrid cross: studying one feature at a time.
- Dihybrid cross: studying two characteristics at a time.

Sex Determination

In most mammals, including humans, XX is female, and XY is male.
Sex is determined by a monohybrid cross.
The cross shows that there is a 50:50 chance of a baby being a boy or a girl.

Incomplete Dominance

In cows, a parent with a red coat and a parent with a white coat produce offspring with a mottle color called roan.
Neither allele is fully dominant since both show in the phenotype.

Linkage

Linked genes are genes that are located on the same chromosome and are therefore inherited together.
If the genes are on the same chromosomes, they will be inherited together.
Crossing over can occur during meiosis, resulting in a small proportion of non-parental phenotypes.### Chromosomal Crossing Over
Involves the swapping of sections of homologous chromosomes during meiosis
Not required to know the details of crossing over

Sex Linkage

Refers to genes found on the X or Y chromosome
These genes are called heterosomes because they are different shapes and sizes
X chromosome carries genes for sex-linked characteristics, such as haemophilia and colour blindness
Y chromosome is relatively empty, but contains genes for sperm production

Haemophilia

A group of diseases where a person's blood does not clot properly
Caused by a lack of a particular protein
Gene for the normal condition is dominant, while the gene for the abnormal condition is recessive
Carrier: a female who has an allele for the abnormal condition but does not show it

Genotypes and Phenotypes in Males and Females

Females:
- XNXN: normal blood clotting
- XNXn: carrier, has normal blood clotting but carries the condition
- XnXn: haemophilia
Males:
- XNY: normal blood clotting
- XnY: haemophilia

Inheritance of Haemophilia

Female carrier (XNXn) and male normal (XNY) parents:
- 25% chance of producing a haemophiliac child
- 50% chance of producing a haemophiliac son
It is the mother who determines if the son is haemophiliac or not, since the father always passes the Y chromosome to his son

Non-Nuclear Inheritance

DNA found in mitochondria and chloroplasts, outside of the nucleus
This DNA is always passed on by the female in the cytoplasm of the ovum (egg)
In animals, the sperm only provides the chromosomal materials, and the mitochondrial DNA is used for energy production
In plants, the pollen grain only contains nuclear DNA, and no mitochondrial or chloroplast DNA is present

Family Tree of Sex-Linked Crosses

Cross A: 2 affected males and 2 carrier females
Cross B: 2 normal males and 2 carrier females
Cross C: 1 affected male, 1 normal male, 1 normal female, and 1 carrier female

Ratios

Monohybrid and Dihybrid crosses:
- Homozygous dominant with homozygous recessive or heterozygous: 3:1 (75%:25%)
- Heterozygous with heterozygous: 1:1 (50%:50%)
- Heterozygous with homozygous recessive: 1:2:1 (25%:50%:25%)
- Heterozygous co-dominant with heterozygous co-dominant: 1:1:1:1 (25%:25%:25%:25%)
- Heterozygous dihybrid with homozygous recessive dihybrid: 9:3:3:1
Sex-linked:
- All offspring normal, all female carriers: XNY- with XNXN
- 50% normal males:50% carrier females: XNY- with XNXn
- 1 affected male, 1 normal male, 1 normal female, 1 carrier female: XNY- with XNXn
- All female carriers and all male offspring are affected: XNY- with XnXn
- All offspring affected: XnY- with XnXn

Variation and Evolution

Variation: the differences between individuals of a species
Causes of Variation:
- Sexual reproduction: independent assortment of homologous chromosomes during meiosis
- Mutations: sudden changes in the amount or structure of DNA
Types of Mutations:
- Chromosome mutations

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Test your knowledge on Mendel's second law, the Law of Independent Assortment, with this quiz! Learn about how factors are randomly distributed during gamete formation and how it relates to the inheritance of traits in organisms. Explore examples such as the crossing of pea plants with different characteristics.

The Law of Independent Assortment

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