Answer:
Gravity.
Explanation:
Gravity is what causes stuff to fall. It also keeps us on the ground, If there were no gravity, life wouldn’t exist as we know it today. Brainliest please! I need brainlest in order to keep answering questions!!
Answer:
1) Homologous chromosomes are chromosomes that are the same in size and shape and control the same characteristics; occur in pairs in higher animals and plants
2) Internal fertilization is a mating pattern in which the male and female come close together, the male introduces the sperm into the body of the female, and fertilization occurs. It is practiced by mammals like goat, sheep etc
3) Pollination is the transfer of pollen from male to female cones in gymnosperms, or from anther to stigma in flowering plants. It is effected by insects, birds, bats and the wind.
4) Zygote is the result of fertilization in which two gametes have fused together; often simply called a fertilized egg.
Answer:
AaBb × aabb
Explanation:
A test cross is a cross between an unknown genotype (dominant phenotype) with a homozygous recessive genotype in order to discover the actual genotype of the species exhibiting dominant phenotype.
This is because one allele of a gene is capable of masking the expression of another, the allele masking is called DOMINANT allele while the allele being masked is called RECESSIVE allele. The combination of these two alleles is termed heterozygosity.
An organism that is phenotypically dominant for a specific trait may either be heterozygous or homozygous for that gene. For example, a plant gene for tallness with an dominant allele T, and recessive allele t. This plant will need tall if the genotype is TT (homozygous dominant) or Tt (heterozygous dominant). In order to know which of these genotypes the plant actually has, a test cross is conducted.
In this example, two genes A and B are involved. For the first gene, A represents dominant allele while a represents recessive allele. For the second gene, B represents dominant allele while b represents recessive allele.
In a cross involving parents AABB (homozygous dominant for both genes) and aabb (homozygous recessive for both genes), the F1 progeny will all exhibit phenotypic dominance (AaBb).
However, we cannot know the genotype by merely looking at the phenotype. We cannot ascertain yet whether the dominance is heterozygous or homozygous, hence the need for a test cross.
The test cross is between the dominant F1 progeny and a homozygous recessive i.e. AaBb × aabb. Some of the F2 generation will show recessive traits if the unknown genotype is heterozygous.
