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Questions and Answers
What is the primary advantage of sexual reproduction in organisms?
What is the primary advantage of sexual reproduction in organisms?
- It eliminates the need for adaptation.
- It ensures identical genetic copies.
- It enhances genetic reshuffling. (correct)
- It requires fewer resources than asexual reproduction.
What occurs during the meiotic prophase?
What occurs during the meiotic prophase?
- Cell membrane divides.
- Homologous chromosomes pair up. (correct)
- Chromosomes are replicated.
- Gametes are formed.
What initiates the process of crossing over during meiosis?
What initiates the process of crossing over during meiosis?
- Separation of sister chromatids
- Replication of chromosomes
- Double-strand breaks in DNA (correct)
- Formation of gametes
In contrast to meiosis, what is a key characteristic of mitosis?
In contrast to meiosis, what is a key characteristic of mitosis?
How does genetic improvement relate to adaptation in changing environments?
How does genetic improvement relate to adaptation in changing environments?
What does independent assortment refer to in the context of gamete formation?
What does independent assortment refer to in the context of gamete formation?
How many different haploid gametes can be formed when n equals 3?
How many different haploid gametes can be formed when n equals 3?
What is the main consequence of nondisjunction during meiosis?
What is the main consequence of nondisjunction during meiosis?
What occurs as a result of crossing over during meiosis?
What occurs as a result of crossing over during meiosis?
Why are no two similar organisms exactly alike in terms of their gametes?
Why are no two similar organisms exactly alike in terms of their gametes?
What is the main advantage of sexual reproduction over asexual reproduction?
What is the main advantage of sexual reproduction over asexual reproduction?
Which of the following best describes parthenogenesis?
Which of the following best describes parthenogenesis?
What term describes the different versions of a gene?
What term describes the different versions of a gene?
What is a gene pool?
What is a gene pool?
Which type of cells are primarily involved in sexual reproduction?
Which type of cells are primarily involved in sexual reproduction?
What does gene frequency refer to?
What does gene frequency refer to?
What is the significance of homologous chromosomes in sexual reproduction?
What is the significance of homologous chromosomes in sexual reproduction?
How does polyploidy differ from diploidy and haploidy?
How does polyploidy differ from diploidy and haploidy?
What mechanism do DNA transposons use to move within the genome?
What mechanism do DNA transposons use to move within the genome?
What is the primary difference between DNA transposons and retrotransposons?
What is the primary difference between DNA transposons and retrotransposons?
Which of the following is NOT a characteristic of simple sequence repeats (SSRs)?
Which of the following is NOT a characteristic of simple sequence repeats (SSRs)?
What primarily constitutes the bulk of the human genome?
What primarily constitutes the bulk of the human genome?
What is one consequence of retrotransposons duplicating themselves?
What is one consequence of retrotransposons duplicating themselves?
How do retrotransposons replicate and move within the genome?
How do retrotransposons replicate and move within the genome?
What is the ultimate goal of cells according to the content?
What is the ultimate goal of cells according to the content?
Which reproductive strategy is generally faster, according to the content?
Which reproductive strategy is generally faster, according to the content?
What is pleiotropy in genetics?
What is pleiotropy in genetics?
How does consanguinity affect genetic diseases?
How does consanguinity affect genetic diseases?
Which of the following describes polygenics in genetics?
Which of the following describes polygenics in genetics?
What does Mendel's Law of Segregation imply?
What does Mendel's Law of Segregation imply?
Why are deleterious dominant mutations rapidly eliminated from the population?
Why are deleterious dominant mutations rapidly eliminated from the population?
Which of the following factors is NOT considered in the study of genetics?
Which of the following factors is NOT considered in the study of genetics?
What characterizes a recessive allele causing disease in a population?
What characterizes a recessive allele causing disease in a population?
Which trait is an example of a condition that follows Mendelian inheritance?
Which trait is an example of a condition that follows Mendelian inheritance?
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Study Notes
Chromosome Pairing and Crossing Over
- Ensures proper segregation of homologous chromosomes during meiosis
- Haploid gametes contain reassorted genetic information due to independent assortment and crossing over
- Independent assortment: Produces 2^n different haploid gametes (n = number of chromosomes)
- Crossing over: Creates limitless genetic variations
- Meiosis is not flawless, nondisjunction (incorrect chromosome separation) occurs in ~10% of egg meiosis and ~3% of sperm meiosis
- Aneuploidy: Condition with abnormal chromosome number
Mendel and the Laws of Inheritance
- Transposable elements (TEs) can move and duplicate within the genome, creating new repetitive DNA sequences
- They do not code for proteins, but play various roles in chromosome structure and function
- The bulk of the human genome consists of repetitive nucleotide sequences and other non-protein-coding DNA
- DNA transposons move via a cut-and-paste mechanism
- Retrotransposons move by copying and pasting using RNA intermediate
- Retrotransposons increase copy number more rapidly than DNA transposons
Benefits of Sex
- Asexual reproduction is fast and produces identical offspring
- Sexual reproduction is slower and leads to genetically diverse offspring
- Parthenogenesis: Oocytes develop without sperm/fertilization
Sexual Reproduction
- Involves diploid and haploid cells
- Most cells are diploid (2n) or haploid (n)
- Somatic cells are diploid, germ line cells are haploid
- Sexual reproduction generates genetic diversity
- Allele: Variant version of a gene
- Gene pool: All genes within a population
- Gene frequency: How often an allele occurs in a gene pool
Genetic Diversity
- Sexual reproduction provides a competitive advantage in a changing environment
- Genetic reshuffling allows adaptation to changing environments
Meiosis
- Special cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes
- Duplicated homologous chromosomes pair during meiotic prophase
- Crossing over occurs between maternal and paternal chromosomes
Chromosome Pairing
- Key process in meiosis
- Homologous chromosomes do not pair in mitosis
- Crossing over is initiated by a double-strand break in one of the interacting DNA strands
- Specialized enzymes for double-strand breaks are not expressed during mitosis
Mendelian Genetics
- Pleiotropy: A single gene affects two or more traits
- Polygenics: Traits determined by multiple genes
- Environmental factors and epigenetics influence gene expression
Mendel's Law of Segregation
- Applies to all sexually reproducing organisms
Pedigrees
- Show the risks of first-cousin marriages
- Recessive alleles causing diseases are rare, making it unlikely for two carriers to meet and mate
- Consanguineous matings increase the chance of both parents carrying the same rare allele
Recessive Mutations
- Most mutations are neutral
- Deleterious dominant mutations are rapidly eliminated from the population
- Recessive mutations remain at low frequency in the population
Classical Genetic Approach
- Begins with random mutagenesis
- Point mutations are less likely to be effective than other types of mutations
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