Chapter 4 Flashcards
Define Heredity
the passing of traits from parents to offsprings
Define Genetics
the branch of biology dealing with heredity and the variation of inherited characteristics
Define Genes
segment of DNA that codes for a particular trait: found at specific locations on a chromosomes
Define Locus
the location of a gene on a chromosome
Define DNA (Deoxyribonucleic acid)
a macromolecule that carries genetic information in cells
Define allele and two types of alleles
Most genes have two or more variations called alleles
- Dominant Allele: An allele that if present, it’s trait is expressed
(ie. Ww or WW)
- Recessive Allele: An allele that is masked by the dominant allele if present recessive trait is only expressed if only recessive alleles are present (ie. ww)
Difference between phenotype and genotype
Phenotype: physical trait and individual shows (ie. widow’s peak)
Genotype: allele combination an individual has (ie. WW, Ww, ww)
Define Mitosis
a process of nuclear division in eukaryotic cells that occurs when a parent cell divides to produce two identical daughter cells
Where does mitosis occur?
Somatic cells (cells of the body)
What are the phases of cell cycle?
Interphase - G1 (growth), S (DNA synthesis), G2 (growth)
Mitosis
Cytokinesis
Prophase - Mitosis
- pairs of sister chromatids
- Chromatin condenses to form chromosomes
- Nuclear membrane breaks down
- Duplicated centrioles migrate to opposite poles
- Spindle fibers begin to form
Metaphase - Mitosis
- Spindle fibers attach to chromosome
- Centromere align along equatorial plate
- Sister chromatids face opposite poles
Anaphase - Mitosis
- Centromere splits
- Sister chromatids are pulled to opposite poles by spindle fibers
Telophase - Mitosis
- Nuclear membrane forms around each set of chromatids
- Spindle fibers disappear
- Chromatids decondense to chromatin
Cytokinesis
- division of cytoplasm
- occurs at the end of mitosis and beginning of interphase
Purpose of Mitosis
- growth
- repair
- maintenance
- asexual reproduction
Types of asexual reproduction
binary fission - asexual where a parent cell results in two identical cells
fragmentation - asexual reproduction where a parent organism breaks into fragments each capable of growing independently into a new organism
budding - asexual reproduction where a new individual develops from some generative anatomical point of the parent organism
vegetation propagation - asexual plant reproduction that occurs in its leaves, roots, and stem
spore formation - plants produce hundreds of spores and the spore sac bursts, spores are dispersed into the air, where they germinate and create a new plant
Biotechnology
use and or modification of an organism for applications in engineering, industry, and medicine
- human benefits
- cloning plants for use in agriculture
Cloning
process of producing one individual that is genetically identical to another, using a single cell or tissue
Plant cloning and 5 types
used to produce strains of plants with identical characteristics and used commercially
- ie. leaf cutting, grafting, stem cuttings, budding, runners
Genetically Modified Organisms (GMO)
genetic material of an organism has been altered using genetic engineering techniques
pros and cons of cloning animals and plants
Plant Cloning
pros
- To produce identical plants quickly and economically
- Effective way of producing new invidiuals from rare and endangered plants, helping to preserve the species
cons
- No genetic variation
Animal Cloning
pros
- Produces healthier animals, which minimizes the use of antibiotics, growth hormones and other chemicals
cons
- Defects in vital organs, such as the liver, brain, and heart
- Seen as unethical
Sexual Reproduction
- each parent contributes a copy of half of its genetic information
- results in being genetically different from parents
- produces genetic variety
Asexual reproduction
- produces offspring genetically identical to a single parent
What are the two key processes of sexual reproduction?
- Formation of haploid sex cell or gametes
- Fertilization, which occurs when two sex cells join to produce a zygote (fertilized egg cell)
What reproductive organs produce what sex cells?
Tests produce sperm in males. Ovaries produce ova (egg cells) in females.
Define meiosis
process where haploid gametes are formed
- chromosomes number of the daughter cells is half of the parent cell
- human cell with 46 chromosomes undergoes meoisis to produce gamete with 23 chromsomes (haploid)
One from Mom one from Dad
- offspring receives complete set of genetic instructions from each parent
- one version from from father and one from mother
Homologous chromosomes
- 23 chromosomes from your father is matched to 23 chromsomes from mother
- paired chromsomes are called homologous chromsomes
- similar in size and shape and carry the genetic info for the same gene
Fertilization
- haploid sperm cell (23) unites with a haploid egg cell (23) to form diploid zygote (46)
- the zygote grows and divides that produces a mature multicellular individual
2 phases of meiosis
- two divisions that produce four haploid cells
- Meiosis I (reduction division) where diploid chromosome number is reduce by half to the haploid chromosome number
- Meiosis II, number of chromsomes i unchanged, total number of cells increase to four
Meiosis I - Prophase I
- DNA replication happens during interphase prior to the start of meiosis
- prophase I, chromosome start to shorten and thicken
- each chromosome consists of two sister chromatids joined at the centromere
- nuclear membrane begins to dissolve, centrioles separate, and move to opposite poles of the cell and spindle fibres form
- chromsomes come together in homologous pairs
- each chromosme of the pair is composed of a pair of sister chromatids
- whole structure called a tetrad beccause each pair of chromosme has four chromatids - each sister chromatid intertwines with a sister chromatid with its matching homologous chromsome, a process called synapsis
- crossing over (mixing of genetic info)
Meiosis I - Metaphase I
- tetrads (made up of pairs of homologoud chromsomes) migrate twoards the centre of the cell and align their centromeres across the middle of the cell
Meiosis I - Anaphase I
- homologous chromosomes move to opposite poles of the cell
- reduction division occurs
- only one chromosome from each homologous pair will be found in each new daughter cell
- each chromosome in the new cell consists of two sister chromatids
Meiosis I - Telophase I
- nuclear membrane begin to form around the chromsomes at each end of the cell and the cell begins to divide
- chromosomes in the two nuclei are not identical
- cells are now haploid
Meiosis II
- begins immediately after telophase I and no duplication of between meiosis I and II
- each haploid daughter cell contains one set of chromosomes
- chromsomes still consist of two sister chromatids that are not identical
Meiosis II - Prophase II
- nuclear membrane dissolves and spindle fibres begin to form
Meiosis II - Metaphase II
- Each with two sister chromatids across the middle of the cell
- sister chromatids remain attached by centromeres
Meiosis II - Anaphase II
- sister chromatids separate and move to opposite poles of the cell
- nuclear membrane begins to form around the chromatids now called chromosomes
Meiosis II - Telophase II
- second nuclear division is completed and the second division of cytoplasm follows
- four genetically different haploid daughter cells (Gametes) have been produced
Random assortment
- a daughter cell can receive either chromosome of each homologous pair called random assortment
- for any diploid (2n) organism the number of combinations is 2^n
- ie. 23 pairs of chromosomes, 2^23=8388608
- does not include added variation from crossing over
Define gametogenesis
- formation of sex cells (haploid) in meiosis
Define spermatogensis
production of sperm cells
- cytoplasm is divided equally during each cell divsion results in four equal sized sperm cells
- small in size and streamlined for maximum motility to be able to swim to an egg cell and fertilize it
Define oogenesis
production of egg cells (ova)
- cytoplasm of the female gametes does not divide equally during each of the two cell division of meiosis
- one daughter cell receives most of the cytoplasm
- other cells, called polar bodies die, and final product is a single ovum (egg cell)
- does not have to be mobile so it can contain a large supply of nutrient in their cytoplasm to fuel future cell division
karyotype
- chromosomes of an individual that have been sorted and arranged according to size and type
- can be used to evaluate chromosomes to diagnose genetic disorder
X and Y chromosomes
- large chromosome is called an X chromosome and smaller chromosome is called a Y chromosome
- XX is female and XY is male
- X chromosomes always come from the mother and father either provides an X or Y chromosome
Define autosomes
- chromosomes that are not sex chromosomes
Difference between euploidy and aneuploidy
euploidy: a cell or organism have an exact multiple of the haploid number
aneuploidy: a cell or organism having an incorrect number of chromosomes
- results in nondisjunction during meiosis
difference between monosomy and polysomy
monosomy = chromosome missing
polysomy = additional chromosomes (ie. trisomy where there are three homologous chromosome in place of a homologous pair)
Nondisjunction in meiosis I and II
meiosis I
- during Anaphase I, no normal gametes will be created
- homologous chromosomes fail to separate
meiosis II
- during anaphase II, half of the gametes will have the correct chromosome number
- sister chromatids fail to separate
Down Syndrome
trisomy 21 - extra homologous chromosome at chromosome 21
Turner syndrome
one X and no Y sex chromosome (X)
Klinefelter syndrome
two X and one Y sex chromosome (XXY)
Patau syndrome
Trisomy 13
Edwards syndrome
trisomy 18
Prenatal testing
- testing for a genetic disorder prior to birth
- recommended for pregnant women over the age of 35 due to increased risk
three Errors in crossing over
insertion/deletion - unequal crossing over between homologous pairs (one missing genes and one extra genes)
inversion - segment of chromosomes rotates before reattaching (genes in incorrect order)
translocation: segment of two non-homologous chromosome crosses over (ie. chromsome 5 crossing over with chromosome 11 instead of two chromosome 5s)
Ways to fix problems with Fertilization
Assisted Reproductive Technologies (ARTS)
- in vitro fertilization - egg cells are combined sperm cells outside the uterus, fertilized egg is then implanted in the uterus and begins pregnancy
- artificial insemination - placing sperm into reproductive tract of a female
non human applications of Assisted Reproductive Technologies (ARTS)
Artificial insemination used in breeding livestock, wild animals, pets
- to enhance genetic diversity and reduce costs by using frozen sperm
- valuable tool to save endangered species
problems
- creating gene banks and related technologies can be expensive
- trying to preserve endangered species in frozen banks may undermine efforts to preserve the species in the wild
