5.1 Flashcards
What is a gene?
A gene is a short length of DNA found on a chromosome that codes for a particular characteristic.
What are alleles?
Alleles are variations of the same gene.
How many alleles do we have for each gene?
.
We have two alleles for each gene
Where do we inherit alleles from?
One allele is inherited from the mother, and the other from the father.
What is phenotype?
Phenotype is the observable characteristic of an organism.
What is genotype?
Genotype is the combination of alleles that control each characteristic.
What is the difference between dominant and recessive alleles?
Dominant alleles only need to be inherited from one parent to show up in the phenotype, while recessive alleles need to be inherited from both parents.
What does homozygous mean?
Homozygous means having two copies of the same allele.
What does heterozygous mean?
Heterozygous means having two different alleles.
How are alleles abbreviated when completing genetic diagrams?
Alleles are abbreviated to single letters, with dominant alleles represented by capital letters and recessive alleles represented by lowercase letters
What is the genome?
The genome is the entire set of genetic material of an organism.
What provides the instructions for making proteins in an organism?
The order of nucleotide base sequences in the DNA provides the instructions for making proteins.
What is the result of the Human Genome Project?
The Human Genome Project has enabled biologists to know the entire human genome, including all genes and their locations in human DNA.
What misconception about dominant and recessive alleles should you avoid?
Whether an allele is dominant or recessive does not affect the mechanism of inheritance; it depends on the proteins they code for, not on dominance or absence.
What is variation?
Variation is defined as differences between individuals of the same species.
What causes phenotypic variation?
Phenotypic variation results from genetic variation (differences caused by genes) and environmental variation (interactions between the organism and its environment).
What are examples of genetic variation in humans?
Examples include blood group, eye color, gender, ability to roll tongue, and whether ear lobes are free or fixed.
What are examples of environmental variation in humans?
Examples include scarring due to accidents, weight gain due to lifestyle, language and accent due to upbringing, and plant growth due to light availability.
What is continuous variation?
Continuous variation occurs when there are many small degrees of difference for a characteristic between individuals, and the data can be measured on a scale. Examples include height, mass, and finger length.
What factors contribute to continuous variation?
Continuous variation is often influenced by both genetic and environmental causes.
What is discontinuous variation?
Discontinuous variation occurs when there are distinct differences for a characteristic, and data fit into discrete categories with no crossover between categories. Examples include blood group, gender, and tongue rolling ability.
What causes discontinuous variation?
Discontinuous variation is usually caused by genetic variation alone
How does continuous data appear on a graph?
Continuous data plotted on a graph typically results in smooth bell curves
How does discontinuous data appear on a graph?
Discontinuous data plotted on a graph typically results in a step-like shape.
What are mutations?
Mutations are changes in the DNA base sequence.
How do mutations impact the genome?
Mutations introduce allele variants into the gene pool, which can impact the genome in various ways.
What are the different outcomes of mutations on proteins?
Mutations may have no effect, may alter the protein without impacting its function, or may significantly alter the protein’s function.
Which scenario of mutations affects the phenotype of an organism?
Mutations that significantly alter the function of proteins can affect the phenotype of an organism
What is gene expression?
Gene expression is the process by which information from a gene is used to synthesize a functional product, typically a protein
What is coding DNA?
Coding DNA refers to the genes of an organism that provide the instructions required to synthesize proteins
What is non-coding DNA?
Non-coding DNA does not code for proteins but can influence protein synthesis through interactions with coding DNA.
How does coding DNA contribute to gene expression?
Only a small proportion of the genes in the genome may be expressed at any time because genes must be activated to be expressed.
How does non-coding DNA influence gene expression?
Non-coding DNA can cause activation or deactivation of genes in the coding DNA, thereby influencing gene expression
What are genetic variants?
Genetic variants are alterations in the DNA sequence resulting from mutations
How do genetic variants impact gene expression?
.
Genetic variants can directly or indirectly influence gene expression by altering the DNA base sequence in coding or non-coding DNA regions of the genome
What happens when a genetic variant alters the DNA base sequence within coding DNA regions?
The mutation may significantly alter the structure of the protein produced, resulting in a non-functional protein. For example, it may affect the enzyme’s active site, making it unable to bind to its substrate.
What are the effects of genetic variants on non-coding DNA regions?
Mutations in non-coding DNA regions can activate or inactivate genes in the coding regions. This can lead to either the transcription of a gene that was previously not being expressed, resulting in the production of a protein, or the halting of transcription of a gene that was previously being expressed, leading to the absence of a protein
What is sexual reproduction?
Sexual reproduction is a process involving the fusion of the nuclei of two gametes to form a zygote, resulting in genetically different offspring.
What are gametes?
Gametes are sex cells, such as sperm and egg cells in animals and pollen cells and egg cells in flowering plants.
What is fertilization?
Fertilization is the fusion of gamete nuclei, resulting in the formation of a zygote.
What is the chromosome number in gametes compared to other body cells?
Gametes contain half the number of chromosomes found in other body cells, making them haploid.
What is the chromosome number in a human gamete?
Human gametes contain 23 chromosomes, while normal body cells contain 46 chromosomes.
How is the chromosome number halved during sexual reproduction?
The chromosome number is halved during meiosis, a process of cell division in reproductive organs that produces gametes.
What are key facts about meiosis?
Meiosis produces four genetically different haploid daughter cells, involves two divisions, and is used to produce gametes
What happens during meiosis I and II?
Before meiosis begins, DNA replication occurs, followed by pairing and alignment of chromosomes in the center of the cell. Then, the cells divide twice to produce four haploid daughter cells.
What is the importance of meiosis?
Meiosis produces gametes and increases genetic variation among offspring by forming new combinations of maternal and paternal chromosomes.
What is asexual reproduction?
Asexual reproduction is a process resulting in genetically identical offspring from one parent, without the involvement of sex cells or fertilization.
What are the characteristics of offspring produced through asexual reproduction?
Offspring produced through asexual reproduction are genetically identical to the parent and to each other, making them clones.
What is the role of mitosis in asexual reproduction?
Only mitosis is involved in asexual reproduction, which ensures the production of genetically identical offspring.
What are some examples of asexual reproduction?
Examples include binary fission in bacteria, budding in plants using bulbs and tubers, and the growth of side shoots called runners in plants like strawberry plants.
What are the key differences between sexual and asexual reproduction?
Differences include the number of parent organisms, the type of cell division required for offspring production, the level of genetic similarity between offspring, the possible sources of genetic variation, the number of offspring produced, and the time taken to produce offspring.
What is monohybrid inheritance?
Monohybrid inheritance involves characteristics controlled by a single gene, resulting in two alleles for each gene inherited from the parents.
What is the phenotype?
The phenotype is the observable characteristics of an organism, such as eye color or blood type.
What is the genotype?
The genotype is the combination of alleles that control each characteristic, usually represented using letters.
What are dominant and recessive alleles?
Dominant alleles show up in the phenotype when inherited from one parent, while recessive alleles require two copies for the characteristic to show.
What is homozygous and heterozygous?
Homozygous individuals have two copies of the same allele, while heterozygous individuals have two different alleles.
How are alleles represented in Punnett squares?
Alleles are abbreviated to single letters, with dominant alleles shown in uppercase and recessive alleles shown in lowercase
What is polygenic inheritance?
Polygenic inheritance involves characteristics controlled by multiple genes, resulting in a wide range of phenotypic combinations.
Give an example of polygenic inheritance.
Eye color is an example of polygenic inheritance, as it is controlled by several genes, resulting in a variety of phenotypes beyond brown and blue.
How is sex determined in humans?
Sex is determined by the 23rd pair of chromosomes, with females having two X chromosomes (XX) and males having one X and one Y chromosome (XY).
How is sex inheritance shown using Punnett squares?
In Punnett squares for sex inheritance, X and Y chromosomes take the place of alleles, with the combination determining the sex of the offspring.
Who was Gregor Mendel?
Gregor Mendel was an Austrian monk who studied mathematics and natural history at the University of Vienna in the mid-19th century.
What did Mendel study in his experiments?
Mendel carried out breeding experiments on plants, particularly pea plants, to study how characteristics were passed on between generations.
What were Mendel’s key experiments with pea plants?
Mendel crossed tall pea plants with dwarf pea plants and then crossed the tall offspring together to observe the inheritance of height characteristics.
What were Mendel’s observations from his experiments?
Mendel observed that each characteristic is determined by hereditary units passed down from each parent unchanged. He showed that the unit for tall plants (T) was dominant over the unit for short plants (t).
What were Mendel’s conclusions about heredity in plants?
Mendel concluded that characteristics are determined by hereditary units passed from parent to offspring unchanged. Offspring receive one unit from each parent, and hereditary units can be dominant or recessive.
What was the importance of Mendel’s work?
Mendel’s work laid the foundation for modern genetics, although its significance was not recognized until after his death. His studies were groundbreaking in the 19th century and provided new insights into inheritance patterns, despite the lack of knowledge about DNA, genes, and chromosomes at the time.
chromosome
threadlike structures of DNA, carrying genetic information in the form of genes. located in the nucleus
features of continuous variation
no distinct classes or categories exist
characteristics can be measured and fall within a range between two extremes
features of discontinuous variation.
distinct classes or categories exist
these characteristics cannot be measured over a range
individuals cannot have features that fall between categories
advantages of sexual reproduction
increases genetic variation
the species can adapt to new environments due to variation, giving them a survival advantage
disease is less likely to affect population
disadvantages of sexual reproduction
takes time and energy to find mates
difficult for isolated members of the species to reproduce
